SPECIFICATIONS  FOR 
STREET  ROADWAY  PAVEMENTS 


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SPECIFICATIONS  FOE 
STREET  ROADWAY  PAVEMENTS 


WITH  INSTRUCTIONS  TO 

INSPECTORS  ON  STREET  PAYING  WORK 


BY 
S.  WHINERY 

MEMBER   AMERICAN   SOCIETY   OF   CIVIL   ENGINEERS 


SECOND  EDITION 
REVISED,  ENLARGED  AND  ENTIRELY  RESET 


McGRAW-HILL  BOOK  COMPANY 
239  WEST  39TH  STREET,  NEW  YORK 

6  BOUVERIE  STREET,  LONDON,  E.  C. 

1913 


COPYRIGHT,  1913,  BY  THE 
MCGRAW-HILL  BOOK  COMPANY 


: ;    :  '';.     : 


THE. MAPLE- PRESS. YORK. PA 


PREFACE  TO  SECOND  EDITION 

In  offering  to  the  public  a  new  edition  of  "Specifications  for 
Street  Roadway  Pavements"  the  author  has  taken  advantage  of 
the  opportunity  to  revise  and  expand  somewhat  the  matter  in  the 
original  edition .  and  to  add  thereto  Instructions  for  Inspectors  on 
pavement  work. 

Since  the  publication  of  the  original  pamphlet  in  1907  no  little 
advance  has  been  made  in  the  design  and  construction  of  street 
pavements  and  the  framing  of  specifications  for  that  work.  Aside 
from  the  personal  study  and  efforts  of  individual  engineers,  the 
Association  for  Standardizing  Paving  Specifications,  organized  in 
the  latter  part  of  1909,  has  held  four  important  conventions,  devoted 
to  the  improvement  and  standardization  of  specifications  for  street 
pavements,  and  its  able  standing  Committees  have  devoted  much 
time  and  thought  to  the  subject.  The  American  Society  of  Muni- 
cipal Improvements  has  also  devoted  much  attention  to  the  subject 
and  has  adopted  standard  specifications  for  most  of  the  common 
kinds  of  pavement.  Other  organizations  have  been  working  along 
the  same  lines. 

Under  these  circumstances  it  might  be  thought  that  there  is  no 
longer  any  pressing  need  for  the  continuance  of  individual  efforts  in 
this  field,  and  it  has  been  with  some  hesitation  that  the  author  has 
returned  to  it.  Without  venturing  to  criticise  the  work  done  by 
these  public  organizations  it  has  seemed  to  the  author  that  there  is  , 
yet  room  for  individual  work  in  this  field,  if  for  no  other  reason 
than  that  there  still  remain  quite  divergent  views  not  only  as  to 
the  substance,  but  as  to  the  form,  scope  and  phraseology  of  speci- 
fications, and  contributions  based  upon  some  knowledge  and  ex- 
perience in  street  pavement  may  not  be  without  value  in  reaching 
final  conclusions. 

As  might  be  expected  experience  and  observation  during  the  past 
five  years  have,  in  a  number  of  particulars,  modified  the  author's 
opinions  and  shown  where  the  original  specifications  offered  might 
be  improved  and  enlarged,  so  that  while,  in  the  main,  those  now 
offered  follow  the  original  text,  the  reader  will  find  not  a  few  changes. 

v 

263620 


vi  PREFACE  TO  SECOND  EDITION 

There  has  also  been  added  specifications  for  two  comparatively  new 
kinds  of  roadway  pavement  that  have  merited  attention,  and  for 
concrete  sidewalk  and  concrete  combined  curb  and  gutter. 

So  far  as  the  author  is  aware  there  has  not  been  printed,  in 
America  at  least,  any  complete  and  comprehensive  code  of  instruc- 
tions for  pavement  inspectors,  though  there  appears  to  be  a  demand, 
as  there  certainly  is  a  need,  for  something  of  the  kind. 

Having  been  asked  about  a  year  since  to  prepare  such  a  set  of 
instructions  for  the  use  of  one  American  city,  the  author  has  re- 
written parts  of  them  in  a  more  general  form,  and  they  are  printed 
(with  the  permission  of  the  engineer  for  whom  they  were  written) 
as  Part  II  of  this  edition.  While  they  would  need  some  revision  and 
modification  to  meet  the  conditions  and  special  specification  pro- 
visions in  any  particular  city,  it  is  thought  they  may  be  useful  in 
at  least  suggesting  the  points  to  be  covered. 


CONTENTS 

PART  I 

SPECIFICATIONS 
Introductory  PAGE 

Value  of  general  specifications i 

Theory  of  specifications i 

Street  paving  work .    .    .  2 

Specifications  should  be  fair  and  just  to  contractor      4 

Relations  of  contractor  to  municipality 6 

Advertisements  for  proposals 7 

Instructions  to  bidders 9 

Relation  between  specifications  and  contract 9 

Specifications 9 

Preparation  of  specifications      .    .    .    r 9 

Engineer  as  arbiter 1 1 

Itemized  unit  prices 12 

SPECIFICATIONS 

General  PAGE  SECTION 

General  description  of  work 13 

Definitions 14                 i 

Changes  in  plans  and  specifications 15                3 

Quality  of  material  and  work 15                 4 

Inspection 15                 5 

Injury  to  persons  and  property 16                 6 

Sanitary  and  public  convenience 16                 7-9 

Disorderly  employees 17  10 

Order  and  progress  of  work 17  n 

Pavement  datum 18  12 

City  monuments  and  stakes      18  13 

Old  and  new  material 18  I4~IS 

Adjusting  street  structures 18  16 

Connection  with  existing  pavements 19  18 

Measurements  and  computations 20  21 

Incidental  and  extra  work 20  23-24 

Guaranty 21  25 

Preparing  the  sub-grade 22  26 

Foundations 

Concrete  foundations — Portland  cement 24  28-29 

Sand 26  30 

Stone 26  31 

Care  of  materials 27  33 

Ratios 27  34 

vii 


viii  CONTENTS 

PAGE  SECTION 

Foundations —  (Continued) 

Mixing  concrete 28  35 

Placing  concrete 29  36 

Setting  of  concrete 29  37 

Foundation  of  old  paving  stone 30  39 

Foundation  of  broken  stone * .    .    .  31  4o~~4I 

Sheet  asphalt  pavement 

General  note 33 

«—  Crude  and  refined  asphalts 36  43~46 

Tempering  agent 38  47 

Sand 38  48 

Pulverized  stone 39  49 

Asphaltic  paving  cement 39  50 

Composition,  surface  mixture 40  51 

Base  course      .    .    .    .    .  42  52-54 

Laying  asphalt  pavement       .    .    . 42  55~58 

Plant 45  59 

Asphalt  block  pavement 

Sub-grade  and  foundation 46  60-6 1 

Asphalt  block i 46  62 

Composition  and  quality 46  63-64 

Laying  blocks 48  66 

Granite  block  pavement 

Granite  blocks .  50  71 

Sand  cushion 51  72 

Setting  blocks 51  73~74 

Filling  joints .  52  75 

Bridge  and  crossing  stone  ......    .  y  ....   .  55  79 

Brick  pavement 

Sub-grade  and  foundation 56  80-8 1 

Paving  brick ......._  ......  56  82-84 

Delivering  brick       58  85 

Sand  cushion 58  86 

Setting  the  brick 59  87-89 

Filling  the  joints      60  90 

Wood  block  pavement 

Sub-grade  and  foundation 62  92~93 

Wood  blocks 63  94 

Creosote  oil 65  95 

Preservative  treatment       65  96 

Laying  wood  blocks 66  97 

Filling  joints 68  98 

Inspection 68  99 

Expansion  joints      68  101 

Bituminous  concrete  pavement 

General  note 69 

Sub-grade  and  foundation     ; 7°  103-109 

*»  Bituminous  concrete  .  71  IIQ 


CONTENTS 


IX 


PAGE  SECTION 

Mixing  and  laying 73  111-112 

Hydraulic  concrete  pavement 

Sub-grade  and  foundation 73  113 

Bottom  course 74  115 

Top,  or  surface,  course 74  116-120 

Expansion  joints      76  121 

Bituminous  surface 77  122 

Experimental  or  Untried  Pavements 78  123-126 

Concrete  Curb  and  Gutter 

General 80  127 

Excavation  and  drainage 81  •  128-129 

Concrete 81  130 

Weather 82  132 

Expansion  joints      .    . 82  133 

Circular  corners 83  134 

Steel  protection 83  135 

Finishing,  forms,  etc 4 83  136-138 

Payment  for 84  139 

Concrete  Sidewalks 

General  note 84 

General  dimensions ;  .  ••-  •  84  140 

Grading 85  141 

Drainage 85  142-143 

Bottom  course 86  144 

Surface  course .  • , 86  145 

Expansion  joints 87  147 

Weather ..- 88  149 

Regrading 88  150 

Repairing  defects 88  151 

Measurement  and  payment 88  152 

PART  II 
INSTRUCTIONS  TO  INSPECTORS 

Introductory  note 91 

General  remarks,  inspection  and  inspectors 91 

General  instructions 94  1-13 

Sub-foundation  work  general ,    .    .    .  96  14 

curbing      97  15 

rough  grading       98  16 

fine  grading 98  17 

incidental  work 98  18 

concrete  foundation 98  19 

quality  of  materials 98  20 

storing  materials      99  21 

proportioning 99  22 

mixing  concrete       100  23 

placing  concrete 100  24-25 

Old  paving  stone  foundation .  101  26 


CONTENTS 

PAGE  SECTION 

Broken  stone  foundation 101  27 

Sheet  asphalt  pavement 101  28 

inspecting  at  paving  plant 102  29-30 

sand 102  3*~33 

refined  asphalt  and  flux      103  34~36 

asphaltic  cement 103  37 

ratio,  sand  and  cement 104  38 

mixing .  104  39 

records       104  40 

Inspecting  on  the  street 105  41-42 

temperature  of  mixture  . ,    .    .  105  43 

preparing  street  surface      105  44 

laying  binder  course 106  45 

laying  surface  course .  ~  106  46-50 

Asphalt  block  pavement 107  Si~52 

Granite  block  pavement .    .  108  53 

blocks 108  54 

sand  cushion .    , 108  55 

setting  the  block      108  56 

ramming  the  blocks 109  57 

filling  joints no  58 

Brick  pavement no 

inspecting  the  brick no  60 

sand  cushion in  61 

setting  brick . in  62 

rolling in  63 

filling  the  joints 112  64-65 

Wood  block  pavement 112 

inspection  of  blocks 112  67 

mortar  bed 112  68 

setting  blocks 113  69 

filling  the  joints 113  70 

Bituminous  concrete  pavement 113  7i~72 

Hydraulic  concrete  pavement 113  73 

foundation 113  74 

surface  course       114  7S~77 

expansion  joints 114  78 

care  of  work 114  79 

Concrete  combined  curb  and  gutter 114 

concrete 115  81 

removing  forms 115  82 

corner  protection 115  83 

patching 116  84 

Hydraulic  concrete  sidewalk 116 

materials 116  86 

drainage 116  87 

two-course  work 116  88 

finishing  surface 1 16  89-90 


PART  I 

SPECIFICATIONS  FOR  STREET  ROADWAY 
PAVEMENTS 


INTRODUCTORY 

In  addition  to  their  value  as  memoranda  and  aids  in  preparing 
specifications  for  a  particular  project,  carefully  prepared  general 
specifications,  embodying  the  latest  approved  practice,  sometimes 
supply  the  most  useful  and  acceptable  brief  treatises  upon  any  par- 
ticular branch  of  engineering  work.  It  has  been  partly  with  this 
thought  in  mind  that  the  following  set  of  specifications  for  standard 
street  pavements  has  been  prepared  and  is  now  offered  to  city 
engineers  and  municipal  authorities. 

To  widen  their  range  and  increase  their  usefulness,  copious  foot 
notes  have  been  added,  referring  to  alternative  requirements  and 
methods  of  construction,  and  giving  some  of  the  reasons  for  the 
preference  or  adoption  of  the  construction  called  for  in  the  speci- 
fications. It  is  recognized  that  in  a  good  many  matters  of  detail 
embraced  in  these  specifications  there  is  difference  of  opinion  among 
able  engineers,  many  of  whom  are  at  least  as  competent  as  the 
writer  to  determine  what  is  best.  They  are  not  offered  in  a  dogmatic 
spirit,  or  with  the  hope  that  all  the  provisions  found  therein  will  be 
accepted.  If  they  shall  be  of  some  assistance  in  bringing  about 
correct  standards  for  such  specifications,  their  preparation  will  have 
been  justified. 

Theoretically,  three  general  classes  of  engineering  specifications 
may  be  noted.  In  the  first,  the  aim  of  the  engineer  is  to  specify  the 
end  or  result  that  it  is  desired  to  secure,  leaving  the  contractor  free 
to  originate  and  follow  the  methods  by  which  these  results  are  to  be 
attained.  In  the  second  the  engineer  aims  to  secure  the  desired 
end  by  specifying  in  detail  the  materials  and  the  methods  which 
in  his  opinion  will  accomplish  the  purpose,  he  himself  assuming 
responsibility  for  the  results.  Either  of  these  two  classes  of  speci- 
fications is  permissible,  and  the  engineer  may  choose  the  one  which 
in  his  opinion  seems  best  adapted  to  the  character  of  the  work  to 
be  done,  and  the  conditions  under  which  it  must  be  prosecuted. 

In  the  third  class  of  specifications,  met  with  more  frequently 
than  they  should  be,  the  engineer  undertakes  to  prescribe  not  only 
the  character  of  the  materials  to  be  used  and  the  methods  to  be 
pursued,  but  also  the  results  to  be  attained.  The  position  thus 
assumed  is  illogical,  and  often  unreasonable,  and  may  lead  to  com- 

1 


2  ••?  STREET  ROA  DWA  Y  PA  VEMENTS 

plications  between  the  engineer  and  the  contractor.  If  a  contractor 
be  required  to  turn  out  a  product  which  shall  conform  to  certain 
standards,  he  may  properly  be  given  much,  if  not  full  latitude,  as 
to  how  the  stipulated  results  shall  be  secured,  and  may  be  held  fully 
responsible  for  the  outcome;  if  on  the  other  hand  the  engineer 
chooses  to  specify  with  more  or  less  minuteness  the  character  of  the 
materials  to  be  used  and  the  methods  of  construction  to  be  followed, 
and  enforces  compliance  therewith,  it  seems  fair  and  just  that  he 
should  assume  responsibility  for  the  results  produced,  and  therefore 
unfair  to  hold  the  contractor  to  responsibility  for  consequences 
arising  from  the  use  of  materials  and  methods  which  he  was  allowed 
no  choice  or  latitude  in  selecting. 

In  street  paving  work,  of  well-known  and  standard  character, 
the  second  class  of  specifications  seems  preferable  for  a  number  of 
reasons,  the  leading  one  being  that  the  time  required  to  develop 
the  good  or  bad  quality  of  the  work  must  usually  extend  over  a  con- 
siderable number  of  years,  and  the  conditions  to  which  the  pavement 
may  be  subjected  in  the  meantime  are  likely  to  vary  so  widely  that 
it  may  be  very  difficult,  if  not  impossible,  to  prescribe  a  satisfactory 
standard  of  service  and  endurance.  Disputes  are  therefore  liable 
to  arise  between  the  municipality  and  the  contractor  as  to  the  latter's 
liability,  or  conditions  may  make  it  difficult  or  impossible  to  hold 
the  contractor  to  strict  account  for  that  liability. 

It  is  believed  that  in  the  present  state  of  the  art  it  is  entirely 
practicable  to  so  frame  specifications  for  the  materials  to  be  used 
and  the  methods  to  be  followed  in  the  construction  of  standard  street 
pavements,  and  to  so  enforce  compliance  therewith,  that  the  engineer 
and  the  municipality  may  safely  assume  responsibility  for  the  quality 
of  the  work  produced.  While  it  may  be  true  that  local  conditions 
sometimes  make  it  very  difficult  to  enforce  compliance  with  speci- 
fications, the  same  conditions  are  likely  to  make  it  at  least  equally 
difficult  to  secure  effective  responsibility  on  the  part  of  the  con- 
tractor for  any  long-period  guarantee  of  the  work  done  by  him; 
and  the  contractor  who  negligently  or  purposely  violates  the  speci- 
fications during  construction  is  not  likely  to  be  more  faithful  or 
scrupulous  in  living  up  to  any  guarantees  he  may  make  with  regard 
to  the  future,  even  where  the  terms  and  conditions  of  such  guar- 
antees may  be  clearly  defined  and  indisputable.  The  writer  has  dis- 
cussed the  subject  of  time  guarantees  as  applied  to  street  pavements 
pretty  fully  in  his  book,  "Municipal  Public  Works,"  and  the  above 
brief  statement  seems  all  that  is  necessary  here. 


INTRODUCTORY  3 

In  conformity  with  this  view  of  the  matter,  the  following  speci- 
fications aim  to  set  out  as  definitely  and  clearly  as  practicable  the 
requirements  for  the  construction  of  good  pavements  of  the  several 
standard  kinds,  and  it  is  assumed  that  the  engineer  will  be  able  to, 
and  will  enforce  them. 

It  is,  however,  not  infrequently  the  case  that  the  engineer  will  be 
called  upon  to  prepare  specifications  for  new,  or  patented,  or  pro- 
prietary pavements  advocated  by  their  promoters,  the  value  or 
usefulness  of  which  have  not  been  sufficiently  established  by  ex- 
perience, and  for  which  the  data  for  detailed,  definite  specifications 
are  not  yet  available. 

In  such  cases  the  wisest  course  to  follow  is  to  confine  the  precise 
specifications  to  the  general  or  standard  parts  of  the  work,  while 
stipulating  only  the  results  to  be  attained  with  regard  to  those  features 
of  the  work  that  are  proprietary  or  questionable,  thus  placing  upon 
the  promoter  or  his  contractors  full  responsibility  for  such  results 
as  are  promised  of  guaranteed.  This  applies  to  new  or  compara- 
tively untried  materials  or  processes,  whether  patented  or  not. 

A  proposed  form  of  general  specifications  to  cover  such  cases  is 
offered  herein. 

It  is  usually  unwise  to  adopt  or  to  incorporate  in  the  municipal 
specifications  those  prepared  or  offered  by  the  promoter  or  patentee, 
which  are  often  brief,  incomplete,  and  indefinite,  and  are  sometimes 
carefully,  and  even  cunningly,  drawn  to  evade  final  responsibility. 

No  attempt  has  been  made  to  submit  specifications  for  proprietary 
or  patented  pavements,  or  those  composed  wholly  or  in  part  of 
materials  which  are  patented  or  protected  by  trade-marks.  The 
owners  or  contractors  engaged  in  constructing  these  pavements, 
often,  if  not  usually,  claim  the  right  to  dictate  the  material  parts 
of  the  specifications  under  which  such  work  shall  be  done,  and  the 
municipal  engineer  who  is  called  upon  to  construct  such  pavements, 
must,  in  each  case,  determine  whether  the  specifications  offered  are 
adequate  and  satisfactory,  and  the  extent  to  which  he  feels  justified 
in  accepting  responsibility  for  the  results.  Naturally,  the  contractor 
or  promoter,  even  if  competent  to  prepare  specifications,  cannot 
be  expected  to  bind  himself  within  closer  limits  than  he  thinks 
necessary  to  secure  the  work.  In  many  such  cases  the  form  of  gen- 
eral specifications  for  "untried  or  experimental  pavements"  given 
herein  might  appropriately  be  used. 

The  engineer  is,  in  common  with  all  men,  fallible,  and  he  can 
hardly  hope,  in  the  preparation  of  specifications,  to  make  them 


4  STREET  ROADWAY  PAVEMENTS 

perfect;  to  cover  every  item  and  particular;  or  to  escape  some 
ambiguities  of  expression,  and  some  degree  of  indefiniteness.  The 
writer  can  only  claim  that  he  has  aimed,  in  the  light  of  a  consider- 
able experience,  to  set  out  as  fully  and  definitely  as  practicable 
the  requirements  for  the  proper  construction  of  high-class  street 
pavements,  and  has  endeavored  to  avoid  loose  or  obscure  terms  and 
expressions.  The  ideal  specification  is  one  that  furnishes  a  wholly 
sufficient  guide  to  the  accomplishment  of  the  desired  purpose;  that 
provides  for  every  possible  contingency  which  may  arise,  and  is 
couched  in  language  which  not  only  means  exactly  what  it  was 
intended  to  mean,  but  is  incapable  of  any  other  interpretation.  It 
is  needless  to  say  that  no  example  of  such  a  perfect  specification 
can  be  instanced  as  a  model. 

It  has  been  the  aim  to  make  these  specifications  fair  and  just 
to  the  contractor;  that  is,  to  require  of  him  no  impracticable  or 
indefinite  service,  or  the  assumption  by  him  of  risks  other  than  those 
fairly  involved  in  the  business  conduct  of  the  work. 

If  the  plans  and  specifications  for  any  work  which  a  contractor 
bids  upon  are  so  full,  specific,  and  clear,  that  he  may  know  exactly 
what  he  will  be  expected  to  do,  and  if  they  do  not  require  him  to 
assume  unusual  chances  and  risks,  he  may  intelligently  name  prices 
which  he  believes  will  compensate  him  for  the  service.  Having 
done  so,  his  proposal  having  been  accepted,  and  a  contract  entered 
into  accordingly,  the  engineer  and  the  municipality  have  a  right 
both  in  law  and  equity  to  demand  that  he  will  do  exactly  and  fully 
what  he  has  contracted  to  do.  No  excuses  on  his  part  can  be  valid 
and  none  should  be  accepted.  He  may  in  all  fairness  and  justness 
be  required  to  "toe  the  mark"  strictly.  To  the  neglect  to  recognize 
and  enforce  these  principles  is  chargeable  the  greater  part  of  the 
poor  and  unsatisfactory  work  so  common  in  street  pavement  work 
in  our  cities.  Unexpected  contingencies  may,  of  course,  arise  where 
some  changes  and  concessions  may  be  proper  and  just,  but  these 
should  be,  and  usually  are,  very  rare.  On  the  other  hand,  sweeping 
general  clauses  in  contracts  and  specifications  intended  to  catch  the 
contractor  "goin'  or  comin',''  unnecessarily  stringent  stipulations 
which  were  never  intended  to  be  strictly  enforced,  but  were  put  into 
the  specifications  with  the  idea  that  they  would  help  hold  the  con- 
tractor up  to  a  high  standard,  and  "one-sided"  contracts  intended 
to  give  the  municipality  an  unfair  advantage  over  the  contractor, 
are  as  inadvisable  in  policy  as  they  are  wrong  in  principle.  Nothing 
should  be  put  in  a  specification  that  is  not  clearly  essential  to  secure 


INTRODUCTORY  5 

the  results  aimed  at,  and,  this  having  been  done,  every  requirement 
should  be  enforced.  The  existence  in  specifications  of  requirements 
that  are  not  intended  to  be  enforced,  gives  the  contractor  a  pretext 
for  neglecting  others  that  may  be  important. 

In  these  specifications  will  be  found  a  number  of  details  that 
are  often  not  regarded  as  important  and  which,  when  found  in  pav- 
ing specifications,  the  contractor  is  frequently  allowed  to  ignore. 
In  the  writer's  opinion,  based  upon  his  experience  in  street  paving, 
every  one  of  these  requirements  is  essential  to  the  production  of 
high-class  work,  which,  it  is  hardly  necessary  to  argue,  is,  in  the  end, 
the  most  economical  work  from  the  standpoint  of  the  municipality. 

It  may  be  argued  that  the  adoption  and  enforcement  of  these 
specifications  would  have  the  effect  of  raising  prices.  In  many  cases 
this  would  doubtless  prove  true.  Contractors  are  entitled  to  a  fair 
and  reasonable  compensation  for  their  services.  It  is  admitted  that 
in  some  cities  the  prevailing  prices  for  some  kinds  of  pavements 
are  below  the  actual  cost  of  the  work  if  it  were  done  in  a  proper 
manner,  conforming  strictly  to  the  specifications.  Illogical  as  it 
undoubtedly  is,  the  low  price  at  which  work  is  taken  is  sometimes 
considered  a  sufficient  reason  for  accepting  work  below  standard. 
The  consequence  is  that  bidders  not  only  count  upon  concessions 
and  lax  enforcement  of  the  specifications,  but  bid  lower  and  lower, 
expecting  that  further  concessions  will  enable  them  to  get  out  with 
an  undeserved  profit.  This  is  one  of  the  most  serious  evils  in  the 
paving  business  to-day,  and  the  highest  public  interests  demand  a 
thorough  reform.  Low  first  cost,  desirable  as  it  may  be,  is  the 
poorest  economy  if  it  be  secured  at  the  sacrifice  of  the  quality  of  the 
work.  If  one  pavement  costs  twenty  per  cent,  more  than  another, 
but  renders  forty  per  cent,  more  service,  it  is  obviously  the  cheaper 
of  the  two. 

Contractors  are  prone  to  contend  that  this  or  that  provision 
in  a  specification  is  unusual,  unnecessary  or  unfair.  In  dealing  with 
them  the  engineer  should  bear  in  mind  that  no  requirement  of  a 
specification  that  is  clearly  and  definitely  stated,  so  that  the  bidder 
may  understand  exactly  what  it  means  and  what  he  will  be  expected 
to  do,  and  may  frame  his  prices  accordingly,  can  be  unreasonable 
or  unfair  to  the  contractor.  Unusual  or  unnecessary  requirements 
may  result  in  unwarrantably  increasing  the  cost  of  the  work,  and 
this  may  raise  a  question  between  the  engineer  and  the  municipality 
employing  him,  but  it  can  furnish  no  occasion  for  questions  of  fair- 
ness or  unfairness  between  the  contractor  and  the  engineer. 


6  STREET  ROADWA  Y  PA  VEMENTS 

The  relations  that  should  exist  between  the  contractee  and  the 
contractor,  and  the  attitude  of  the  engineer  toward  the  contractor 
have  been  widely  discussed  and  are  quite  well  understood  from  both 
the  ethical  and  legal  standpoint. 

It  is  well  to  bear  in  mind  that  when  a  contract  is  duly  entered 
into,  both  the  parties  thereto  are  equal  before  the  law.  Neither  can 
impose  upon  the  other  terms  or  conditions  that  are  not  clearly  in- 
cluded in  or  to  be  fairly  inferred  from  the  contract  itself.  The 
assumption  that  either  party  has  superior  or  extra  rights  not  ex- 
pressed or  to  be  fairly  inferred  from  the  written  agreement,  or  in 
accordance  with  the  established  rulings  of  the  courts,  is  wholly 
without  warrant.  The  smallest  contractor  is,  in  this  respect,  upon 
an  equal  footing  with  the  largest  city  government  for  which  he  may 
undertake  to  do  contract  work.  It  is  not  infrequently  the  case  that 
the  city  assumes  a  superior  and  dictatorial  attitude  not  in  harmony 
with  these  principles,  and  it  is  too  common  for  the  contractor  to  seek 
to  evade  or  to  escape  fiom  clear  contractural  obligations.  In  neither 
case  is  the  action  warranted  by  fairness,  justice,  or  law. 

It  should  be  needless  to  say  that  the  attitude  of  the  engineer 
toward  the  contractor  should  be  one  of  unyielding  and  uncompro- 
mising requirement  that  the  contract  and  specifications  shall  be 
fully  and  faithfully  complied  with,  but  at  the  same  time  one  of 
absolute  fairness  and  even  helpfulness  to  the  contractor.  The  ideal 
relation,  which  should  be  more  commonly  attainable  than  it  appears 
to  be,  is  that  of  helpful  cooperation  to  bring  about  the  results  the 
contract  and  specifications  were  intended  to  secure. 

In. line  with  the  principles  here  outlined  some  observations  upon 
the  preparation  of  contracts  and  specifications  are  appropriate. 

It  is  the  general  practice  to  include  in  and  make  a  part  of  "The 
Contract"  (herein  for  convenience  called  The  General  Contract) 
all  the  various  documents  that  are  supposed  to  relate  directly  to 
the  transaction  as  a  whole.  The  separate  parts  of  such  a  general 
contract  may  vary  in  number  or  character,  but  the  principal  ones 
are  the  following: 

1.  The  advertisement  for  proposals. 

2.  Instructions  to  bidders. 

3.  The  proposal  submitted. 

4.  The  contract  proper. 

5.  The  specifications. 

Each  of  these  should  be  drawn  to  cover  fully  and  clearly  its 
appropriate  purpose  or  function  but  nothing  more.  It  is  not  unusual 


INTRODUCTORY  7 

to  find,  even  in  the  instructions  to  bidders,  stipulations  that  properly 
belong  in  the  contract  or  specifications,  and  it  is  quite  common  to 
find  in  the  contract  proper  a  lot  of  matter  that  properly  belongs  in 
the  specifications  only.  In  such  cases  there  is  liable  to  be  more  or 
less  confusion  as  to  the  actual  meaning  or  requirements  of  the 
general  contract  as  a  whole,  which  may  lead  to  serious  misunder- 
standings and  complications  between  the  parties  thereto.  The 
several  documents  composing  the  general  contract  are  likely  to  be 
prepared  by  different  persons,  looking  at  the  transaction  from 
different  points  of  view,  and  often  not  wholly  familiar  with  the  scope, 
intent  and  language  of  the  other  documents.  There  is  therefore 
a  possibility,  at  least,  of  indefinite,  if  not  of  conflicting  expressions 
which  are  open  to  different  interpretations,  particularly  in  the 
light  of  special  or  unexpected  conditions  that  may  arise  during  the 
progress  of  the  work  or  the  settlement  therefor.  It  would  tend  to 
eliminate  or  avoid  the  possibility  of  such  complications  if  each  of 
the  several  documents  confined  itself  strictly  to  its  appropriate 
function  in  the  general  contract. 

Advertisements  for  proposals  may  be  divided  into  two  general 
classes.  The  one  is  brief  in  form  and  substance,  simply  stating 
that  proposals  for  a  certain  named  work  will  be  received  at  a  stated 
place  and  time,  and  referring  those  interested  to  documents  on  file 
at  a  stated  place  for  all  further  information.  This  is  the  general 
form  adopted  by  the  United  States  War  Department  for  the  many 
projects  carried  out  by  contract  under  its  direction.  A  sample 
advertisement  taken  from  a  current  technical  journal  is  as  follows; 

TREASURY    DEPARTMENT,    OFFICE    OF 

the  Supervising  Architect,  Washington,  D.  C., 
October  10,  1912.  Sealed  Proposals  will  be  received 
at  this  office  until  3  o'clock  p.  m.  on  the  ist  day  of 
November,  1912,  and  then  opened,  for  an  electric 
passenger  elevator  in  the  United  States  post  office, 
Bellingham,  Wash.,  in  accordance  with  the  drawing 
and  specification,  copies  of  which  may  be  had  at  this 
office  at  the  discretion  of  the  Supervising  Architect. 
OSCAR  WENDEROTH,  Supervising  Architect. 

The  other  general  class  of  advertisement,  very  commonly  used 
by  municipal  corporations,  is  much  longer  and  more  elaborate, 
giving  a  condensed  statement  of  the  character  of  the  work  to  be 
done,  the  conditions  under  which  proposals  are  invited  and  will  be 
received,  and  a  schedule  of  the  quantities  of  work  involved,  together 


8  STREET  ROA  DWA  Y  PA  VEMENTS 

with  other  particulars.     A  typical  example  of  such  an  advertise- 
ment, taken* from  the  same  periodical,  is  here  given: 

PUMPING  MACHINERY— ROSELAND 
PUMPING  STATION 

DEPARTMENT  OF  PUBLIC  WORKS 

CHICAGO,  ILL.,  October  2,  1912. 

Sealed  proposals  will  be  received  by  the  City  of 
Chicago  until  n  A.  M.  Wednesday,  October  30, 
1912,  at  Room  406,  City  Hall,  for  furnishing  and 
erecting  at  Roseland  Pumping  Station  one  vertical 
triple  expansion  crank  and  fly  wheel  pumping  engine 
of  a  capacity  of  twenty-five  million  (25,000,000)  gal- 
lons per  day  against  a  normal  head  of  one  hundred 
and  forty  feet  (140').  This  proposal  also  includes 
the  dismantling  of  a  similar  engine  now  at  Lake  View 
Pumping  Station,  transporting  and  erecting  it  at 
Roseland  Pumping  Station,  together  with  the  furnish- 
ing and  erection  of  certain  auxiliaries  and  appurte- 
nances, according  to  plans  and  specifications  on  file  in 
the  office  of  the  Department  of  Public  Works  of  said 
city,  Room  406,  City  Hall. 

Proposals  must  be  made  out  upon  blanks  furnished 
at  said  office,  and  be  addressed  to  said  Department, 
indorsed  "Proposals  for  Pumping  Machinery,  Rose- 
land  Pumping  Station,"  and  be  accompanied  with 
Five  Thousand  ($5,000)  Dollars  in  money  or  a  certi- 
fied check  for  the  same  amount  on  some  responsible 
bank  located  and  doing  business  in  the  City  of  Chi- 
cago and  made  payable  to  the  order  of  the  Commis- 
sioner of  Public  Works. 

•»  The  Commissioner  of  Public  Works  reserves  the 

right  to  reject  any  or  all  bids.  A  deposit  of  One 
Hundred  Dollars  ($100)  will  be  required  to  insure 
safe  return  of  the  plans. 

No  proposal  will  be  considered  unless  the  party 
offering  it  shall  furnish  evidence  satisfactory  to  the 
Commissioner  of  Public  Works  of  his  ability,  and 
that  he  has  the  necessary  facilities  together  with 
sufficient  pecuniary  resources  to  fulfill  the  conditions 
of  the  Contract  and  Specifications,  provided  such 
Contract  should  be  awarded  to  him. 

Companies  or  firms  bidding  will  give  the  individual 
names  as  well  as  the  name  of  the  firm  with  their 
address. 

L.  E.  McGANN, 
Commissioner  of  Public  Works. 


INTRODUCTORY  9 

Such  advertisements  as  this  may  be  required  by  statutes  or  ordi- 
nances, and  in  that  case  are,  of  course,  proper  and  necessary.  Even 
where  not  so  required  they  may  be  considered  advantageous,  be- 
cause they  give  prospective  bidders  more  complete  information  as 
to  the  character  and  magnitude  of  the  work,  and  may  enable  them 
to  decide  at  once  whether  they  care  to  pursue  the  matter  further. 
But  on  the  whole,  the  shorter  form  of  advertisement,  if  permissible, 
seems  preferable,  because  it  refers  the  enquirer  directly  to  the  origi- 
nal and  official  sources  of  information,  the  forms  to  be  used,  the  con- 
tract, specifications  and  estimated  quantities  of  work,  exactly  as 
they  will  and  must  be  presented  to  all  bidders,  and  as  they  will  ap- 
pear in  the  subsequent  stages  of  the  transaction,  and  leaves,  there- 
fore, no  room  for  possible  confusion  of  statements  between  the 
advertisement  and  the  other  documents.  Furthermore,  the  cost 
of  the  shorter  form  of  advertisement  is  much  less,  and  this  is  often 
a  matter  of  some  importance. 

Instructions  to  bidders  should  be  confined  strictly  to  such  in- 
formation and  directions  as  the  bidder  may  need  to  properly  and 
intelligently  make  up  and  submit  his  proposal  in  accordance  with 
the  requirements  relating  thereto.  This  should  include  primarily, 
a  reference  to  the  contract  and  specifications  for  all  general  and  de- 
tailed information  about  the  work  to  be  done,  but  should  carefully 
avoid  any  statements  or  language  that  might  be  construed  to  add 
to,  take  from,  limit  or  modify  the  contract  or  specifications.  Per- 
haps the  briefest  and  best  statement  of  what  this  document  should 
or  should  not  contain  is  that  it  should  be  so  framed  that,  except  as 
a  matter  of  record,  its  office  and  usefulness  should  absolutely  end 
with  the  award  and  signing  of  the  contract. 

No  one  who  is  not  a  lawyer  can  presume  to  say  just  what  the  con- 
tract proper  should  contain  or  cover,  particularly  as  this  may  vary 
with  the  requirements  of  statutes  and  ordinances  in  force  in  a  given 
city.  It  would  seem  logical  and  proper,  however,  to  separate  the 
special  functions  of  contracts  and  specifications  in  such  a  way  that 
each  should  cover  a  distinct  field  of  its  own,  and  be  free  from  en- 
croachment upon  the  proper  domain  of  the  other.  With  such  a 
conception  of  the  proper  domain  of  each,  one  might  safely  say  that 
the  contract  should  undertake  to  set  out  only  the  legal  and  con- 
tractural  relations  of  the  parties  thereto,  and  should  refer  to  the 
plans  and  specifications  for  all  detailed  instructions  as  to  the  actual 
performance  of  the  work  and  the  results  to  be  secured. 

In  the  preparation  of  specifications  for  any  public  work  the  main 


10  STREET  ROADWA  Y  PA  VEMENTS 

points  to  be  kept  in  mind  are  fulness,  definiteness,  and  exact  ex- 
pression. While  brevity  and  conciseness  are  desirable  qualities 
in  any  document,  they  should  not  be  secured  at  the  expense  of  com- 
pleteness and  precision  of  statement.  Even  the  frequent  repeti- 
tion of  words,  phrases  and  sentences  throughout  a  document,  where 
it  is  necessary  to  avoid  the  possibility  of  misunderstanding  or  ambi- 
guity, should  be  resorted  to  freely.  Exact  description  and  defini- 
tion are  more  important  than  literary  style,  though  they  may  often 
be  successfully  combined.  Of  course,  it  is  not  possible  or  necessary 
to  go  into  minute  detail  with  regard  to  every  part  of  the  work. 
Certain  things  may  be  safely  assumed  to  be  required  by  established 
practice  or  trade  usage.  If,  for  instance,  it  is  specified  that  certain 
lumber  shall  be  "dressed"  this  word  has  a  well-understood  meaning 
in  the  trade  and  it  is  unnecessary  to  stipulate  how  the  dressing  shall 
be  done  or  its  character  or  quality,  though  it  may  be  necessary  to 
say  whether  it  is  to  be  dressed  on  one  or  more  sides. 

The  proper  preparation  of  specifications  for  any  work  involves 
a  clear,  distinct  and  complete  conception,  determination  and  design 
of  what  is  to  be  done;  of  the  conditions  that  are  likely  to  be  met  with 
in  carrying  it  out;  and  of  alternate  plans  that  these  conditions  may 
necessitate.  This  may  not  always  be  possible,  for  the  engineer  is 
not  omniscient.  But  careful  study  and  maturity  of  design  will 
enable  him  to  avoid  the  great  majority  of  such  indefinite  expres- 
sions as  "or  in  such  other  manner  as  the  engineer  may  direct,"  "in 
accordance  with  the  instructions  of  the  engineer,"  etc.  A  great 
many  of  the  items  to  which  such  expressions  are  intended  to  and 
do  apply  in  practice,  could  be  definitely  settled  before  the  specifica- 
tions are  prepared  and  thus  all  uncertainty  on  the  part  of  both  engi- 
neer and  contractor  be  avoided.  To  illustrate:  specifications  for 
block  pavement  commonly  stipulate  that  the  blocks  shall  be  set 
in  rows  running  at  right  angles  to  the  axis  of  the  street,  except  at 
street  intersections,  where  the  engineer  may  direct  them  to  be  laid 
at  a  different  angle.  There  is  usually  no  good  reason  why  the  engi- 
neer should  not  determine  beforehand  at  which,  if  any,  stieet  inter- 
sections the  general  rule  should  be  changed  and  so  state  in  the  specifi- 
cations. These  may  be  and  usually  are  unimportant  matters  which 
may  not  much  affect  one  way  or  the  other  the  cost  to  the  contractor. 
But  they  often  prove  otherwise,  and  the  contractor  is  entitled  to 
know  when  he  submits  his  proposal  just  what  he  will  be  requiied  to 
do.  Of  course  it  may  develop  during  the  progress  of  the  work  that 
changes  from  the  original  plan  will  become  necessary,  but  these  should 


INTRODUCTORY  11 

be  provided  for  in  some  such  definite  and  previously  stipulated 
manner  as  outlined  in  Sect.  3  of  the  following  specifications. 

The  practice  of  inserting,  either  in  the  specifications  or  the  con- 
tract, a  clause  making  the  engineer  judge  and  arbiter  in  any  differ- 
ences that  may  arise  between  the  city  and  the  contractor,  and  pro- 
viding that  his  decision  in  all  such  cases  shall  be  final,  is  as  unwise 
as  it  is  often  illegal.  Such  clauses  are  based  on  the  assumption  that 
the  engineer  is  a  competent  as  well  as  a  disinterested  party  in  the 
transaction,  an  assumption  that  is  usually  wholly  wrong,  though  to 
their  honor  it  may  be  said  that  the  confidence  thus  reposed  in  engi- 
neers is  seldom  abused.  But  the  fact  is  that  the  engineer  is 
never  actually  a  disinterested  party.  He  is  employed  and  paid  by 
the  city  to  look  after  its  interests,  and  is  under  no  obligations  to  the 
contractor  other  than  those  named  in  the  contract  and  specifica- 
tions and  his  sense  of  justice,  propriety  and  professional  honor.  He 
would  be  recreant  to  his  duty  if  in  all  nicely  balanced  matters  of 
doubt  he  did  not  espouse  the  side  of  his  employer.  Moreover,  his 
personal  interests  are  often  involved.  Having  prepared  the  plans, 
specifications  and  estimates  for  the  work,  he  is  naturally  and  properly 
anxious  that  it  shall  be  successful  and  that  the  cost  shall  not  exceed 
that  estimated.  Under  all  these  conditions  it  is  hardly  possible 
for  any  human  being  to  be  a  wholly  disinterested  and  unprejudiced 
judge.  No  broad-minded  and  conscientious  engineer  desires  to 
be  placed  in  such  a  difficult  position,  and  it  is  as  unfair  as  it  is  un- 
wise and  improper  to  require  him  to  assume  it. 

There  are,  however,  a  number  of  matters  of  fact  in  reference  to 
which  it  is  proper  and  necessary  to  make  the  judgment  and  decision 
of  the  engineer  controlling  and  final,  unless  it  may  be  shown  that 
his  decision  is  clearly  erroneous  or  affected  by  improper  motives, 
or  by  fraud.  Some  one  must  necessarily  be  made  the  immediate 
and  final  judge  as  to  whether  the  quality  of  materials  and  work- 
manship is  in  accordance  with  the  requirements  of  the  plans  and 
specifications,  and  as  to  the  quantity  of  work  actually  performed, 
and  these  duties  and  responsibilities  are  very  properly  placed  upon 
the  engineer. 

It  not  infrequently  occurs  that  specifications  are  not  drawn  as 
clearly  as  they  should  be  in  the  matters  of  methods  of  measuring 
the  work  and  of  applying  contract  unit  prices,  and  indefiniteness 
and  carelessness  in  this  regard  are  often  a  source  of  misunderstand- 
ing and  dispute  between  the  engineer  and  the  contractor.  It  is  a 
good  practice,  followed  by  many  able  engineers,  after  specifying 


12  STREET  ROADWA  Y  PA  VEMENTS 

how  a  certain  part  of  the  work  shall  be  done,  to  state  how  it  shall 
be  measured  and  paid  for  at  the  contract  unit  prices. 

In  many  respects  it  is  desirable  that  all  the  work  to  be  done  under 
contract  should  be  quite  fully  itemized,  and  a  unit  price  named  for 
each  kind  of  work.  It  is  the  custom  in  many  cities  to  name  only 
certain  leading  items  of  the  work  to  be  done  under  a  paving  con- 
tract, as  for  the  pavement  complete,  furnishing  and  setting  new 
curbing,  redressing  and  resetting  old  curbing,  and  possibly  a  few 
other  leading  items,  and  to  require  that  all  necessary  incidental 
work  shall  be  done  by  the  contractor  without  cost  to  the  city;  or,  in 
other  words,  he  must  take  this  possible  extra  work  into  considera- 
tion in  naming  his  unit  prices  for  the  leading  items  of  the  work. 
As  the  quantity  of  this  incidental  work  is  often  not  stated,  and  the 
contractor  has  no  means  of  ascertaining  it,  he  must  guess,  as  intelli- 
gently as  he  may  be  abJe,  how  much  he  should  add  to  his  unit  prices 
to  cover  its  cost.  If  he  is  a  prudent  contractor  he  will  be  sure  to 
add  enough  to  prevent  any  possible  loss  on  this  account.  In  most 
cases  the  quantities  of  this  incidental  work  can  be  determined  and 
scheduled  by  the  engineer  with  the  more  important  items,  and  the 
contractor  may  be  required  to  name  unit  prices  for  it.  True,  there 
are  likely  to  develop  during  the  progress  of  the  work  some  items 
that  could  not  be  forseen  or  that  were  overlooked.  In  some  cities 
such  contingencies  are  provided  for  by  a  clause  in  the  contract  or 
specifications  scheduling,  by  name,  all  the  incidental  minor  items 
of  work  that  experience  has  shown  are  likely  to  be  met  with  in  street - 
paving  contracts,  and  naming  fair  unit  prices  which  the  contractor 
will  be  paid  for  each,  should  it  occur.  The  contractor  may  then 
feel  assured  that  however  much  the  quantity  of  such  incidental 
work  may  vary,  he  will  receive  compensation  proportionate  thereto, 
and  he  may  name  his  prices  for  the  main  items  with  more  confidence. 
Under  such  conditions  it  is  reasonable  to  expect  closer  figures  than 
he  would  be  willing  to  name  if  an  unknown  quantity  of  incidental 
work  for  which  no  separate  pay  is  provided  had  to  be  taken  into 
consideration. 

Sub-division  of  unit  prices  is  also  desirable  in  order  that  the  engi- 
neer may  be  able  to  analyze  and  record  the  elements  that  make  up 
the  aggregate  cost  of  the  work.  Thus,  in  the  case  of  the  construc- 
tion of  a  new  sheet-asphalt  pavement  it  is  common  to  ask  for  a  single 
price  for  the  pavement  complete,  including  a  five  year  guarantee. 
Now  the  work  will  consist  of  several  distinct  operations  or  kinds 
of  work  for  each  of  which  a  separate  price  might  be  named: 


SPEC  IF  1C  A  TIONS  1 3 

1.  The  grading  of  the  street  and  preparation  of  the  sub- grade. 
The  quantity  of  this  work  will  vary  on  different  streets  and  is  best 
reckoned  by  the  cubic  yard  of  material  excavated. 

2.  A  price,  either  per  cubic  yard  or  per  square  yard  for  the  con- 
crete foundation. 

3 .  A  price  per  square  yard  for  the  asphalt  pavement  proper.     This 
might,  if  desired,  be  sub-divided  into  separate  prices  for  the  base 
course  and  the  surface  course. 

4.  A  price  per   square  yard  for  guaranteeing  the  pavement  for 
five  years. 

Such  sub-division  would,  it  is  true,  increase  the  work  of  final  com- 
putation but  if  of  no  other  value,  the  detailed  costs  would  be  a  great 
aid  to  the  engineer  in  estimating  the  reasonable  cost  of  future  work 
where  the  relative  quantity  of  these  detailed  parts  varied. 


SPECIFICATIONS 

For  Grading  and  Paving,  or  Repaving 

with Pavement 

on  a Foundation,  the  Roadway 

of 

Street,  from 

to , 

together  with  work  incidental  thereto. 


GENERAL  DESCRIPTION  OF  WORK 

The  work  embraced  in  and  to  be  done  under  this  contract  con- 
sists of  grading  the  entire  street  from  curb  to  curb  between  the 
limits  named,  including  the  removal  or  readjustment  of  the  pave- 
ment now  on  the  roadway,  setting  and  resetting  curbing,  laying 
or  relaying  sidewalks  where  required,  furnishing  all  new  material 
and  performing  all  the  labor  required  for  paving  the  roadway, 
together  with  all  incidental  work  necessary  to  complete  the  whole 
in  a  proper  manner,  in  accordance  with  the  contract,  the  plans  on 


14  STREET  ROADWAY  PAVEMENTS 

file  in  the  office  of  the  City  Engineer,  these  Specifications  and  the 
instructions  of  the  City  Engineer,  herein  referred  to  as  the  Engineer, 
or  his  authorized  agents. 

REFERENCES 

The  numbered  divisions  of  these  specifications  are  herein  desig- 
nated as  "sections,"  each  being  referred  to  by  the  number  standing 
at  its  beginning.  Where  reference  is  herein  made  to  any  such  section 
number  it  shall  be  considered  equivalent  to  a  quotation  of  that 
section. 

The  plans  and  drawings  relating  to  this  work,  on  file  in  the 
office  of  the  City 'Engineer  are  designated  as 

1.  Authority. — Wherever,  in  these  specifications,  the  words,  the 
City,  are  used,  they  shall  be  understood  to  refer  to  the  duly  consti- 
tuted municipal  government  of  the  city  of 

or  its  authorized  agents,  acting  within  the  authority  specifically  con- 
ferred upon  them  by  the  said  municipal  government.1 

Wherever,  in  these  specifications,  the  words,  the  Engineer,  shall 
be  used,  they  shall  be  understood  to  refer  to  the  City  Engineer 
of  said  city,  or  his  deputies  or  assistants,  acting  within  the  authority 
conferred  upon  them  by  the  City  Engineer. 

But  no  agent  of  the  city  shall  have  power  to  revoke,  alter,  enlarge 
or  relax  the  stipulations  or  requirements  of  these  specifications, 
except  in  so  far  as  such  authority  may  be  specifically  conferred  in 
or  by  the  specifications  themselves,  without  the  formal  authorization 
so  to  do,  conferred  by  the  contract  of  which  these  specifications 
are  a  part,  or  by  ordinance,  resolution  or  other  usual  official  action 
of  the  city.2 

2.  Interpretation. — In  case  of  any  actual  or  alleged  disagreement 
or  discrepancy  between  the  contract,  these  specifications,  and  the 
plans  for  the  work  on  file  in  the  office  of  the  Engineer,  the  language 

1  In  specifications  to  be  used  in  any  particular  city  the  official  name  of  the 
city  government,  as  the  City  Council,  the  Commissioners  of  Public  Works, 
etc.,  should  be  used  instead  of  this  general  designation. 

2  Such  a  proviso  as  this  seems  proper  in  justice  to  both  the  city  engineer  and 
the  contractor;  the  former  should  not  be  held  responsible  for  the  acts  of  his 
assistants  when  they  transcend  the  authority  conferred  upon  them,  and  the 
latter  should  be  put  upon  his  guard  with  reference  to  requirements  which  he  is 
not  satisfied  are  sanctioned  or  approved  by  the  city  engineer. 


SPECIFICATIONS  15 

and  provisions  of  the  contract  shall  take  precedence  and  prevail; 
and  the  Engineer  shall  determine  in  each  case  whether  the  specifica- 
tions or  the  plans  shall  be  followed. 

3.  The  Engineer  shall  have  the  right  to  make  such  changes  in  the 
plans  and  specifications  of  the  work  as  he  may  deem  necessary  or 
desirable  or  to  provide  for  unexpected  conditions  or  contingencies 
that  may  develop  at  any  time  after  the  signing  of  the  contract,  or 
during  the  progress,  or  before  the  final  acceptance  of  the  work; 
provided  that  all  such(changes  do  not  involve  an  aggregate  increase 
or  decrease  in  the  cost  of  the  work,  as  shown  by  his  estimates,  of 
more  than  ten  (10)  per  cent.     The  contractor  shall  accept  such 
changes  when  made,  as  a  part  of  the  original  contract  and  specifica- 
tions, subject  to  all  the  provisions  and  conditions  thereof.     But 
before  any  such  changes  shall  become  valid  and  before  the  contractor 
shall   begin   the  particular   work  involved  in   such   changes,   the 
increased  or  decreased  cost  of  the  work  by  reason  of  such  changes, 
above  or  below  what  it  would  have  been  under  the  original  plans 
and  specifications,  shall  be  agreed  upon  in  writing  between  the 
engineer  and  the  contractor.     And  when  the  whole  work,  including 
such  changes,   shall  have  been  completed  and  accepted  by  the 
engineer,  the  sum  or  sums  so  agreed  upon  shall  be  added  to  or 
deducted  from  the  sum  that  would  have  been  due  the  contractor 
if  no  such  changes  had  been  made. 

4.  Quality  of  Material  and  Work. — The  judgment  and  decision 
of  the  Engineer  as  to  whether  the  materials  supplied  and  the  work 
done  under  this  contract  comply  with  the  requirements  of  these 
specifications,  shall  be  conclusive  and  final.     No  material  shall  be 
used  in  the  work  until  it  has  been  examined  and  approved  by  the 
Engineer,  or  his  authorized  agents.     All  rejected  material  must  {be 
promptly  removed  from  the  work  and  replaced  with  that  which  is 
acceptable  to  the  Engineer,  and  all  improper  or  defective  work  must 
be  corrected,  and,  if  necessary,  removed  and  reconstructed  so  as  to 
comply  with  these  specifications  and  the  instructions  of  the  Engineer. 

In  all  matters  of  detail  not  specifically  covered  by  the  specifica- 
tions the  work  shall  be  well  and  skillfully  done  in  accordance  with 
the  best  trade  or  art  customs  and  standards  for  work  of  like  character 
and  purpose. 

5.  Inspection. — The  Engineer  may  provide  for  the  inspection,  by 
assistants  and  inspectors  under  his  direction,  of  all  materials  used 
and  all  work  done  under  this  contract.     Such  inspection  may  extend 
to  all  or  any  part  of  the  work,  and  to  the  preparation  or  manufacture 


1 6  STREET  ROA  DWA  Y  PA  VEMENTS 

of  materials  to  be  used,  whether  within  the  limits  of  the  work  on  the 
street,  or  at  any  other  place.  The  Engineer  and  his  inspectors  shall 
have  free  access  to  all  parts  of  the  work,  including  mines,  quarries, 
manufactories,  or  other  places  where  any  part  of  the  materials  to  be 
used  is  procured,  manufactured  or  prepared.  The  Contractor  shall 
furnish  the  Engineer  all  information  relating  to  the  work  and  the 
material  therefor  which  the  Engineer  may  deem  necessary  or  perti- 
nent, and  with  such  samples  of  materials  as  may  be  required.  The 
Contractor  shall,  at  his  expense,  supply  inspectors  with  such  labor 
and  assistance  as  may  be  necessary  in  the  handling  of  materials 
for  proper  inspection.  Inspectors  shall  have  authority  to  reject 
defective  material  and  to  suspend  any  work  that  is  being  improperly 
done,  subject  to  the  final  decision  of  the  Engineer.  Inspectors  shall 
have  no  authority  to  permit  deviations  from,  or  to  relax  any  of  the 
provisions  of  these  specifications  without  the  written  permission  or 
instruction  of  the  Engineer;  nor  to  delay  the  Contractor  by  failure 
to  inspect  materials  and  work  with  reasonable  promptness. 

The  payment  of  any  compensation,  whatever  may  be  its  charac- 
ter or  form,  or  the  giving  of  any  gratuity,  or  the  granting  of  any 
valuable  favor,  by  the  Contractor  to  any  inspector,  directly  or 
indirectly,  is  strictly  prohibited,  and  any  such  act  on  the  part  of 
the  Contractor  will  constitute  a  violation  of  these  specifications.1 

6.  Injuries  to  Persons  and  Property. — The  Contractor  shall  be 
held  alone  responsible  for  all  injuries  to  persons,  and  for  all  damages 
to  the  property  of  the  city  or  others,  caused  by  or  resulting  from  the 
negligence  of  himself,  his  employees  or  agents,  during  the  progress 
of,  or  connected  with  the  prosecution  of  the  work,  whether  within 
the  limits  of  the  work,  or  elsewhere.     He  must  restore  all  injured 
property,  including  side-walks,  curbing,  sodding,  pipes,  conduits, 
sewers  and  other  public  or  private  property  to  a  condition  as  good 
as  it  was  when  he  entered  upon  the  work. 

7.  Sanitary   Conveniences;   Nuisances. — The    Contractor   shall 

1  It  may  be  objected  that  this  requirement  is  unusual  and  unnecessary,  since 
such  practices  are  recognized  as  wrong,  and  as  presumptive  of  fraud  and  mal- 
practice on  the  part  both  of  the  contractor  and  the  inspector.  It  cannot,  how- 
ever, be  denied  that  in  many  cities  such  means  are  employed  by  contractors  to 
unduly  influence  the  action  of  inspectors  and  that  not  infrequently  the  latter  not 
only  accept,  but  persistently  demand,  valuable  considerations  from  the  con- 
tractor. Silence  of  the  specifications  on  this  point  cannot,  of  course,  be  con- 
strued into  consent,  but  there  is  no  good  reason  for  the  silence.  There  should 
be  left  no  excuse  for  misconception  of  the  position  of  the  city  or  of  the  engineer 
upon  this  point. 


SPECIFICATIONS  17 

provide  all  necessary  privy  accommodations  for  the  use  of  his  em- 
ployees on  the  street,  and  shall  maintain  the  same  in  a  clean  and 
sanitary  condition.  He  shall  not  create  nor  permit  any  nuisance 
to  the  public  or  to  residents  in  the  vicinity  of  the  work. 

8.  Public    Convenience. — No    material,    or    other    obstruction 
shall  be  placed  within  five  feet  of  fire  hydrants,  which  must  be  at 
all  times  readily  accessible  to  the  Fire  Department. 

During  the  progress  of  the  work  the  convenience  of  the  public 
and  of  the  residents  along  the  street  must  be  provided  for  as  far  as 
practicable.  Convenient  access  to  driveways,  houses  and  build- 
ings along  the  street  must  be  maintained  wherever  possible.  Tem- 
porary approaches  to  and  crossings  of  intersecting  streets  and  side- 
walks must  be  provided  and  kept  in  good  condition,  wherever 
practicable. 

9.  Barriers,  Lights,  Watchmen. — The  Contractor  shall  provide 
and  maintain  such  fences,  barriers,  " street  closed"  signs,  red  lights, 
and  watchmen  as  may  be  necessary  to  prevent  avoidable  accidents 
to  residents  and  to  the  public. 

10.  Disorderly  Employees. — Disorderly,  intemperate,  or  incom- 
petent persons  must  not  be  employed,  retained,  or  allowed  upon 
the  work.     Foremen  or  workmen  who  neglect  or  refuse  to  comply 
with  the  instructions  of  the  Engineer,  shall,  at  his   request,  be 
promptly   discharged,    and   shall   not   thereafter    be  re-employed 
without  his  consent. 

1 1 .  Order  and  Progress  of  Doing  Work. — The  work  under  this  con- 
tract shall  be  prosecuted  at  as  many  different  points,  at  such  times, 
and  in  such  sections  along  the  line  of  the  work,  and  with  such  forces 
as  the  Engineer  may  form  time  to  time  deem  necessary,  and  direct, 
to  secure  its  completion  within  the  contract  time.     Not  more  than 
one  thousand  (1,000)  linear  feet  of  the  street  shall  be  torn  up,  ob- 
structed or  closed  to  travel  at  any  one  time  without  the  written  per- 
mission of  the  Engineer.     Completed  portions  of  the  pavement 
shall  be  opened  to  travel  as  directed  by  the  Engineer,  but  such 
opening  shall  not  be  construed  as  an  acceptance  by  the  City  of  the 
work  done.     Where  thus  opened  to  public  travel  by  the  direction 
of  the  Engineer,  the  Contractor  will  not  be  held  responsible  for  in- 
juries to  the  work  caused  by  such  travel  or  public  use,  pending  the 
final  completion  and  acceptance  of  the  whole  work. 

12.  Grade   and    Contour   of   Pavement. — Roadway   pavements 
shall  be  laid  to  such  grades,  crown  and  contour  of  surface  as  the  plans 
may  show  or  the  Engineer  may  direct,  and  the  surface  of  the  com- 


18  STREET  ROADWA  Y  PA  VEMENTS 

pleted  pavement  shall  conform  accurately  to  such  grades,  crown 
and  contour.  The  designed  surface  of  the  completed  pavement 
shall  be  considered  as  the  datum  or  plane  of  reference  in  fixing  the 
location  or  level  of  the  sub-grade,  of  the  pavement  foundation,  and 
of  structures  connected  therewith.  It  will  be  hereafter  referred  to 
in  these  specifications  as  ''The  pa vement  datum. " 

13.  City  Monuments  or  Stakes. — The  Contractor  must  carefully 
protect  from  disturbance  or  injury  all  city  monuments,  stakes  and 
benchmarks,  and  shall  not  excavate  nearer  than  five  feet  to  any  of 
them  without  the  permission  of  the  Engineer;  or  until  they  have 
been  removed,  witnessed,  or  otherwise  disposed  of  by  the  Engineer. 

14.  Old  Material. — All  material  or  structures  removed  from  the 
street  and  not  required  for  the  new  construction,  but  which  the  city 
may  desire  to  reserve,  shall  be  delivered  and  neatly  piled  up  in  a 
corporation  yard  or  elsewhere,  by  the  Contractor,  as  the  Engineer 
may  direct.     Such  reserved  material  shall  be  considered  in  the 
custody  of  the  Contractor  until  delivered  at  the  place  designated, 
and  he  will  be  held  responsible  for  its  care  and  protection,  and  must 
make  good  any  losses  occasioned  by  damage,  theft,  or  misappro- 
priation whlie  it  is  on  the  street  or  en  route  to  the  place  of  storage. 
If  the  Contractor  shall  be  required  to  haul  such  reserved  material 
more  than  one-half  mile,  he  shall  be  paid  a  reasonable  price,  to  be 
agreed  upon  in  advance,  for  the  haul  exceeding  that  distance. 

Material  taken  from  the  work  which  is  to  be  used  in  the  new  con- 
struction shall  be  compactly  piled  where  it  will  least  obstruct  the 
sidewalks  or  adjoining  sections  of  the  street,  and  properly  protected 
by  the  Contractor  until  it  is  required  for  use. 

All  old  material  removed  from  the  work,  including  the  material 
excavated  in  preparing  the  sub-grade,  not  reserved  by  the  City  nor 
to  be  used  again  in  the  work,  shall  belong  to  the  Contractor  and 
must  be  removed  by  him  from  the  street  as  promptly  as  possible. 
It  must  not  be  placed  on  the  sidewalks  or  adjacent  streets,  nor  on 
any  other  street  or  property  belonging  to  the  City,  nor  on  the  prop- 
erty of  private  owners,  without  the  written  consent  of  the  Engineer, 
or  the  owner  of  the  property. 

15.  Storage  of  New  Material. — The  material  for  construction 
when  brought  upon  the  street  shall  be  neatly  piled  so  as  to  cause  as 
little  obstruction  to  travel  as   possible,    and   so  that  it   may  be 
conveniently  inspected. 

1 6.  Rebuilding  and  Adjusting  Street  Structures. — Catch  basins, 
manhole,  sewer  and  water  frames  and  covers,  sewer  inlets,  water 


SPECIF  1C  A  TIONS  1 9 

pipes  and  other  conduits,  belonging  to  the  City  and  within  the  limits 
of  the  work,  shall,  if  necessary,  be  reset  to  the  new  lines  and  grades 
of  the  street  and  for  this  purpose  good  brick  masonry  of  the  original 
thickness,  laid  in  Portland  cement  mortar  shall  be  used.  Great 
care  must  be  taken  to  set  all  such  structures  as  project  through 
the  pavement  exactly  to  the  grade  and  contour  of  the  new  street 
surface,  and  any  defects  in  the  conformity  of  such  structures  to 
the  pavement  datum,  discovered  at  the  time,  or  during  the  progress 
of  the  work,  or  during  the  guaranty  period,  stipulated  in  Sec.  25 
shall  be  promptly  remedied  by  the  Contractor. 

17.  Clean  Sidewalks. — During  the  progress  of  the  work,   the 
sidewalks  and  portions  of  the  street  adjoining  the  work,  or  in  its 
vicinity,  must  not  be  obstructed  or  littered  more  than  may  be  abso- 
lutely necessary,  and  the  adjacent  sidewalks  must  be  kept  clean. 

1 8.  Connection  With  Existing  Pavements  or  Streets. — Wherever 
a  new  pavement  joins  or  abuts  against  an  existing  pavement  of  a 
different  kind,  or  an  unpaved  street,  either  at  the  end  of  the  new 
pavement  or  at  cross  or  intersecting  streets,  a  line  of  stone  headers 
shall  be  provided  and  set.     The  stone  shall  be  of  sound,  hard  lime- 
stone, sandstone,  granite  or  bluestone,  free  from  injurious  imper- 
fections.    The  separate  stones  shall  be  not  less  than  three  (3)  feet 
long,  at  least  eighteen  (18)  inches  deep,  not  less  than  four  and  one- 
half  (4  1/2)  inches  wide  at  the  top,  nor  less  than  three  (3)  inches 
wide  at  the  bottom.     The  top  shall  be  of  uniform  width  for  each 
line  of  headers,  and  shall  be  dressed  square  and  even.     The  ends 
shall  be  dressed  to  secure  a  joint  not  wider  than  one-half  (1/2)  inch 
for  a  depth  of  six  inches  from  the  top,  and  the  sides  dressed  so  as  to 
secure  good  contact  and  close  jointing  with  the  pavement.     The 
stones  shall  be  set  accurately  with  their  tops  at  the  pavement  datum, 
on  a  bed  of  concrete  nine  (9)  inches  wide  and  six  (6)  inches  deep, 
and  after  being  set  the  trench  shall  be  filled  and  rammed  full  of 
gravel  or  crushed  stone. 

All  existing  pavements  adjoining  or  abutting  against  the  new 
pavement,  with  their  crosswalks,  curbs,  and  gutters,  shall  be  ad- 
justed, or  taken  up  and  relaid,  to  conform  to  and  connect  with  the 
pavement  datum,  to  such  an  extent  as  the  Engineer  may  direct. 

Where  the  new  and  adjoining  pavement  are  of  the  same  kind, 
and  headers  are  not  used,  the  new  and  the  old  pavement  must  be 
properly  joined  and  connected,  as  the  Engineer  may  direct. 

Stone  headers  will  be  paid  for  by  the  linear  foot  at  the  contract 
price  for  that  item,  and  the  other  work  embraced  in  this  section 


20  STREET  ROADWA  Y  PA  VEMENTS 

will  be  paid  for  at  the  contract  prices  for  the  several  items,  where 
such  contract  prices  are  provided;  otherwise  the  work  shall  be  con- 
sidered as  incidental  work  and  shall  be  done  at  the  expense  of  the 
Contractor. 

19.  Curbing  to  be  Completed  in  Advance. — The  setting  of  all 
new  curbing  and  guttering  and  the  redressing,  resetting  or  readjust- 
ment of  all  old  curbing  must  be  completed  at  least  100  feet  in  advance 
of  the  construction  of  the  street  foundation. 

20.  Final  Cleaning  Up. — Immediately  after  the  completion  of 
the  work,  or  any  consecutive  portion  of  it,  the  Contractor  shall  re- 
move from  it  all  unused  material,  refuse  and  dirt  placed  by  him 
on,  or  in  the  vicinity  of  the  work,  or  resulting  from  its  prosecution, 
and  restore  the  street  to  a  condition  as  clean  as  before  the  work  was 
begun ;  and  the  new  pavement  shall  be  properly  cleaned. 

21.  Measurements   and   Computations. — Unless   otherwise   dis- 
tinctly provided  in  the  contract  and  specifications,  measurements 
computations  and  payments  will  be  based  upon  the  actual  quantities 
of  completed  work,  customary  or  conventional  mehtods  of  measure- 
ment and  computation  to  the  contrary  notwithstanding. 

The  area  of  street  pavement  shall  be  reckoned  in  square  yards 
of  completed  pavement  surface,  deducting  manholes,  inlets  and  other 
openings  in  the  surface  of  the  pavement  having  an  area  of  over 
three  (3)  square  feet.  Unless  separately  paid  for  under  the  con- 
tract stone  headers  and  crosswalks  will  be  measured  as  a  part  of  the 
pavement  surface. 

22.  The  price  for  the  pavement  per  square  yard  shall,  unless 
otherwise  stated  herein,  include  the  preparation  of  the  sub-founda- 
tion, the  construction  of  the  foundation,  the  cushion  course,  and 
the  pavement  complete,  including  all  the  materials  and  labor  re- 
quired therefor. 

23.  Incidental  Work  at  Contractor's  Expense. — All  the  work  to  be 
done  by  the  Contractor  for  which  specific  unit  prices  are  not  named 
in  the  contract,  specified  and  enumerated  in  Sections  4,  5,  6,  7,  8,  9, 
12,  13,  14,  15,  16,  17,  18,  19,  and  20,  as  well  as  any  minor  details 
of  work  not  specifically  mentioned  in  the  specifications,  but  obviously 
necessary  for  the  proper  completion  of  the  work,  shall  be  considered 
as  incidental,  and  as  being  a  part  of  and  included  with  the  work 
for  which  prices  are  named  in  the  contract.     The  Contractor  will 
not  be  entitled  to  any  extra  or  additional  compensation  therefor. 

24.  Extra   Work. — The    City   may   require    the    Contractor    to 
furnish  such  additional  materials  and  to  do  such  additional  work, 


SPECIFICATIONS  21 

not  provided  for  in  the  contract  and  these  specifications,  but  which 
may  be  found  necessary  or  pertinent  to  the  proper  prosecution  and 
completion  of  the  work  embraced  in  the  contract,  at  prices  to  be 
agreed  upon  in  writing,  in  advance.  But  no  work  other  than  that 
included  in  the  contract  and  these  specifications  and  which  is  covered 
by  and  to  be  paid  for  at  the  prices  named  in  the  contract,  shall  be 
done  by  the  Contractor  except  upon  a  written  order  from  the  Engi- 
neer, which  order  shall  describe  the  work  to  be  done  and  name 
the  compensation  agreed  upon  therefor.  In  the  absence  of  such 
written  order  from  the  Engineer  the  Contractor  will  not  be  entiteld 
to  payment  for  any  such  additional  or  extra  work. 

In  the  same  manner  the  city  may  omit  or  dispense  with  items  or 
parts  of  the  work,  by  previous  agreement  with  the  contractor,  and 
a  like  written  order  by  the  engineer.  But  such  additions,  omissions 
or  alterations  shall  not  together  increase  or  decrease  the  aggregate 
cost  of  the  whole  work  more  than  fifteen  per  cent.  (15%).  Any 
changes  in  the  plans,  specifications,  character  of  material  used  or 
method  of  doing  the  work  that  may  increase  or  decrease  the  aggre- 
gate cost  of  the  work  more  than  fifteen  per  cent.  (15%)  may  be 
authorized  and  validated  only  by  a  formal,  supplemental  contract, 
regularly  executed  by  all  the  parties  to  the  original  contract.1 

25.  Guaranty.2 — The  Contractor  shall  guarantee  that  all  the  ma- 
terials used  and  all  the  work  done  under  this  contract  shall  fully 
comply  with  the  requirements  of  these  specifications,  the  plans 
herein  before  referred  to  and  the  instructions  of  the  Engineer.  Any 
defects  in  the  completed  work,  or  any  part  of  it,  or  any  failure  of  the 
work  to  fully  perform  or  endure  the  service  for  which  it  was  intended, 

1  This  section  is  intended  as  much  for  the  control  and  limitation   of   city 
officials  as  of  contractors.     The  practice  of  carelessly  or  purposely  allowing 
municipal  contracts  to  be  expanded  greatly  beyond  the  stated  limits  or  the 
original  intended  volume  and  cost  without  formal  authorization  by  the  proper 
municipal  body  in  which  the  power  to  make  contracts  is  lodged,  is  dangerous 
and  wrong  and  should  be  prohibited.     In  one  instance  coming  to  the  notice  of 
the  author  a  contract  originally  intended  to  cover  $50,000  worth  of  work  was 
expanded  by  the  department  head  without  any  authority  from  the  city  council 
until  the  final  estimate  reached  the  enormous  sum  of  over  $400,000. 

2  As  outlined  in  the  introduction,  these  specifications  are  designed  to  secure 
the  construction  of  the  pavement  in  a  proper  manner,  the  city  assuming  responsi- 
bility for  the  character  and  utility  of  the  work.     The  guarantee  here  proposed  is 
therefore  intended  to  cover  only  a  proper  compliance  with  the  specifications,  for 
which  the  contractor  may  properly  be  held  responsible,  and  not  the  sufficiency 
or  utility  of  the  work,  if  constructed  according  to  the  specifications.     The  pe- 
riod of  guaranty  should  therefore  be  short,  not  exceeding  two  years. 


22  STREET  ROADWA  Y  PA  VEMENTS 

which,  in  the  opinion  of  the  Engineer,  are  attributable  to  the  use 
of  materials,  skill,  or  workmanship  not  in  compliance  with  the  said 

specifications,  plans  and  instructions,  within  a  period  of 

years  after  the  date  of  the  certificate  of  completion  and 

acceptance,  shall  be  regarded  as  prima  facie  and  conclusive  evidence 
that  the  Contractor  has  failed  to  comply  with  the  said  specifications, 
plans  and  instructions.  And  the  Contractor  shall,  at  his  own  ex- 
pense, at  such  time  and  in  such  manner  as  the  Engineer  may  direct, 
repair  or  take  up  and  reconstruct  any  such  defective  work,  in  full 
compliance  with  the  original  specifications,  plans  and  instructions. 
And  as  surety  for  the  performance  of  this  guaranty  the  Contractor's 
bond,  required  by  the  contract,  shall  remain  in  full  force  until  the 
expiration  of  the  period  of years  above  stipu- 
lated in  this  section. 

PREPARING  THE  SUB-GRADE 

26.  Grading. — The  whole  area  to  be  occupied  by  the  pavement 
and  its  foundation  shall  be  excavated  or  filled  up  to  a  sub-grade  at 
such  an  alevation  that  after  being  compacted  by  the  roller,  the 

surface  will  be inches  below  the  pavement  datum,  and  truly 

parallel  thereto.  In  excavating,  the  earth  must  not  be  disturebd 
below  the  sub-grade.  Plowing  will  not  be  permitted  where  the  depth 
of  earth  to  be  removed  is  less  than  five  (5)  inches,  and  in  no  case  must 
the  plow  be  allowed  to  penetrate  to  within  less  than  one  inch  of  the 
sub-grade.  Places  that  are  found  to  be  loose,  or  soft,  or  composed 
of  unsuitable  material,  below  sub-grade,  must  be  dug  out  and  refilled 
with  sand,  or  other  material  as  good  as  the  average  of  that  found  on 
the  street. 

Where  the  natural  surface  of  the  ground  shall  be  below  the  sub- 
grade,  or  shall  become  so  by  the  removal  of  old  pavement  or  other 
structures,  it  must  be  filled  to  the  sub-grade  in  layers  not  exceeding 
five  inches  in  depth,  and  each  layer  shall  be  thoroughly  rolled  or 
rammed  before  the  next  layer  is  placed  upon  it,  and  when  the  filling 
is  completed  the  filled  area  must  be  properly  trimmed  and  com- 
pacted by  rolling  or  ramming  to  the  true  sub-grade,  as  in  excavation. 
The  material  excavated  from  the  street  may  be  used  for  such  filling, 
provided  it  be  of  suitable  quality.  Where  it  cannot  be  thus  procured 
from  the  street  it  must  be  obtained  by  the  Contractor  elsewhere,  in 
which  case  the  actual  quantity  so  obtained,  measured  after  it  is  com- 
pacted in  the  street,  will  be  paid  for  at  the  contract  price  for  "earth 


SPECIFICATIONS  23 

filling."  The  price  bid  for  "earth  excavation"  will  be  paid  for  all 
material  excavated  above  the  sub-grade,  measured  in  place  on  the 
street,  which  price  includes  the  cost  of  disposing  of  the  excavated 
material,  whether  as  waste  or  filling,  and  of  trimming  and  rolling 
or  ramming  the  sub-grade,  and  of  making  it  ready  for  the  pavement 
foundation. 

After  the  excavation  is  completed  and  the  surface  neatly  trimmed, 
the  whole  area  shall  be  well  compacted  by  rolling  with  a  roller  weigh- 
ing not  less  than  five  tons.  Areas  inaccessible  to  the  roller  shall 
be  rammed  until  they  are  as  well  compacted  as  the  rolled  surface. 
When  the  rolling  is  completed  the  surface  must  be  nowhere  more 
than  three-fourths  inch  below,  norjjmare)  than  three-eighths  inch 
above  the  true  sub-grade.  If,  after  the  rolling  is  completed  and 
before  the  pavement  foundation  is  laid,  the  surface  shall  become 
disturbed  in  any  way,  it  must  be  replaced  and  properly  compacted. 

Where  the  soil  composing  the  sub-foundation  is  found  to  be  wet 
or  "springy,"  a  system  of  soft  tile  drains,  discharging  into  the  street 
drainage  system,  shall  be  constructed  by  the  Contractor,  as  directed 
by  the  Engineer.  The  tile  shall  be  laid  in  trenches  about  one  foot 
wide  and  from  one  to  two  feet  deep.  After  the  tile  is  in  place  the 
trenches  shall  be  filled  with  crushed  stone  or  gravel,  well  compacted 
by  tamping.  The  tile  will  be  paid  for  per  linear  foot  at  the  contract 
price  for  the  same,  which  price  shall  include  the  cost  of  excavating 
and  refilling  the  trenches  with  crushed  stone. 

PAVEMENT  FOUNDATION 

27.  Pavement  foundation  shall  consist  of  hydraulic  concrete, 
or  of  old  pavement  stone  relaid,  or  of  broken  stone  or  gravel,  as 
may  be  herein  specified,  constructed  upon  the  sub-grade.1 

1  In  the  great  majority  of  cases  the  most  satisfactory  and,  in  the  end,  the 
most  economical  foundation  for  a  pavement  is  hydraulic  cement  concrete.  Old 
paving-block  foundation,  if  constructed  as  specified  in  Sect.  36,  will  give  results 
equally  as  satisfactory,  but  if  a  fair  market  exists  for  the  blocks  taken  up  from 
the  street,  it  will  usually  be  found  more  economical  to  sell  them  and  construct 
a  concrete  foundation  for  the  new  pavement.  Broken  stone  or  gravel  founda- 
tions may  serve  the  purpose  fairly  well  upon  a  street  of  light  travel,  but  it  should 
never  be  used  on  streets  of  considerable  or  heavy  travel.  Its  lower  first  cost  is 
the  only  thing  in  its  favor,  but  this  will,  in  nearly  every  case,  be  more  than  offset 
by  the  better  service  and  greater  durability  of  the  pavement,  even  on  streets  of 
light  travel,  if  laid  upon  an  adequate  hydraulic  concrete  foundation.  Proper 
repairs  to  pavement  surfaces  cut  into  for  pipe  work,  etc.,  are  difficult  to  make 
and  hardly  ever  satisfactory  over  broken  stone  foundation  for  the  reason  that 


24  STREET  ROADWAY  PAVEMENTS 

HYDRAULIC  CONCRETE    FOUNDATION 

28.  Concrete. — Concrete  shall  be  composed  of  Portland  cement, 
sand,  broken  stone  and  water. 

29.  Portland  Cement.1 — Portland  cement  shall  be  denned  as  the 

the  lack  of  cohesion  in  the  material  allows  it  to  loosen  or  crumble  away  from 
under  the  edge  of  the  pavement  surface,  and  it  is  difficult  to  restore  it  to  its 
original  solidity  and  strength.  The  first  cost  saved  by  its  use  is  usually  not 
great;  for  whenever  its  use  would  be  permissible  at  all,  a  comparatively  thin  and 
lean  concrete  would  give  better  results,  at  a  very  slight  increase  in*  cost.  To 
illusrtate:  On  a  suburban  street  with  light  travel  a  concrete  foundation  four 
inches  in  thickness,  the  concrete  made  with  Portland  cement  in  the  ratio  of  i 
cement,  4  sand,  and  8  stone,  would  be  stronger  and  in  every  way  better  than  a 
foundation  eight  inches  in  depth  of  broken  stone.  At  the  usual  prices  of  mater- 
ials and  labor,  the  former  may  cost  about  $0.46  per  sq.  yd.,  and  the  latter  about 
$0.40  per  sq.  yd.;  but  for  the  latter  there  would  be  required  1/9  cu.  yd.  more 
sub-foundation  excavation,  worth  about  four  cents,  so  that  the  equivalent  cost 
would  be  $0.44  per  sq.  yd.  The  difference,  two  cents  per  sq.  yd.,  is  insignificant 
when  compared  with  the  greater  value,  better  service,  and  greater  durability  of 
a  pavement  on  the  concrete  foundation.  It  is  sometimes  held  that  the  broken 
stone  foundation  provides  necessary  sub-drainage.  But  all  the  standard  pave- 
ments are,  or  soon  become,  impermeable  to  water  from  the  surface,  and  seepage 
from  the  sub-foundation  can  be  better  taken  care  of  by  the  sub-drainage  specified 
in  Sect.  26,  which  should  usually  cost  not  more  than  five  cents  per  square  yard 
of  the  pavement;  and  if  drainage  be  required,  these  sub-drains  should  be  used 
even  with  the  broken  stone  foundation. 

The  practice  of  laying  pavement  surfaces,  particularly  those  of  asphalt,  upon 
a  foundation  of  old  stone  blocks,  carelessly  reset,  with  the  joints  unfilled  with 
mortar,  is  all  wrong  and  should  never  be  resorted  to.  The  integrity  and  dura- 
bility of  an  asphalt  pavement  depends  largely  ypon  the  strength  and  rigidity  of 
its  foundation;  to  lay  an  asphalt  surface,  however  good,  over  such  an  old  block 
foundation,  is  an  inexcusable  waste  of  money. 

Old  stone  block  and  cobble-stone  pavements,  that  have  become  solidified  in 
place  by  long  travel  over  them,  make  a  good  foundation  for  asphalt  or  other 
pavements,  provided  they  can  be  utilized  without  taking  up  or  disturbing  the 
old  pavement;  but  such  cases  occur  so  rarely  that  they  have  not  been  considered 
in  these  specifications. 

A  thoroughly  consolidated  old  McAdam  pavement,  if  not  worn  too  thin,  also 
makes  a  very  satisfactory  pavement  foundation  if  it  can  be  used  undisturbed,  or 
by  simply  trimming  off  the  high  points. 

Low  places  in  old  pavements,  that  are  otherwise  satisfactory  for  a  foundation, 
may  be  brought  to  the  proper  elevation  with  hydraulic  concrete.  "Binder" 
material  is  usually  specified  for  this  purpose  in  foundations  for  asphalt  pavements, 
but  hydraulic  concrete  is  both  better  and  cheaper. 

1  The  specifications  for  Portland  cement  here  given  are  practically  those 
adopted  by  the  "American  Society  for  Testing  Materials," 

Natural  Cement.  While  these  specifications  uniformly  refer  to  the  use  of 
Portland  cement,  it  is  not  intended  to  convey  the  idea  that  natural  cement  concrete 


SPECIFICATIONS  25 

pulverized  product  resulting  from  the  calcination  to  incipient  fusion 
of  an  intimate  mixture  of  properly  proportioned  argillaceous  and 
calcareous  materials,  and  to  which  no  addition  greater  than  three 
per  cent,  has  been  made  subsequent  to  calcination. 

Specific  Gravity. — The  specific  gravity  of  the  dry  cement  at  a 
temperature  of  two  hundred  and  twelve  (212)  degrees  F.  shall  not 
be  less  than  3.10. 

Fineness. — It  shall  be  pulverized  to  such  fineness  that  not  more 
than  eight  (8)  per  cent,  shall  fail  to  pass  a  number  one  hundred 
(100)  sieve  and  not  more  than  twenty-five  (25)  per  cent,  shall  fail 
to  pass  a  number  two  hunbred  (200)  sieve. 

Time  of  Setting. — At  the  temperature  of  sixty  (60)  degrees  F. 
mortar  made  of  neat  cement  shall  not  begin  to  set  in  less  than  thirty 
(30)  minutes,  nor  set  hard  in  less  than  one  hour,  but  must  set  hard 
within  ten  (10)  hours. 

Strength. — When  thoroughly  mixed  dry  with  clean,  sharp,  mod- 
erately coarse  sand,  in  the  ratio  by  weight  of  one  part  cement  to 
three  parts  of  sand,  and  then  made  into  stiff  mortar,  briquets 
made  from  this  mortar  and  exposed  for  one  day  to  moist  air  and 
immersed  in  water  for  the  balance  of  the  periods  named  below, 


is  not  suitable  for  pavement  foundations;  on  the  contrary,  it  may  be  used  with 
entire  confidence,  as  the  experience  in  a  large  number  of  cities  has  proven  beyond 
question.  Whether  Portland  or  natural  cement  shall  be  used  is  usually  a  ques- 
tion of  relative  cost.  At  the  present  very  low  prices  of  Portland  cement  in  most 
cities,  more  strength  in  pavement  foundations  can  usually  be  obtained  per 
dollar  expended  for  cement,  from  Portland  than  from  natural  cement.  The 
specifications  for  natural  cement,  as  adopted  by  the  American  Society  for 
Testing  Materials  differ  from  those  for  Portland  cement  in  the  following 
particulars:. 

The  specific  gravity  shall  not  be  less  than  2.8. 

Fineness.  The  residue  left  on  a  No.  100  sieve  shall  not  exceed  10  per  cent., 
and  on  a  No.  200  sieve  shall  not  exceed  30  per  cent. 

Setting.  It  shall  not  begin  to  set  in  less  than  ten  minutes,  nor  set  hard  in 
less  than  thirty  minutes;  but  shall  set  hard  within  three  hours. 

Tensile  Strength  (per  sq.  in.). 

Neat.  24  hours  in  moist  air 5°  to  IO°  l^5- 

7  days  (i  day  in  air,  6  days  in  water) 100  to  200  Ibs. 

28  days  (i  day  in  air,  27  days  in  water) 200  to  300  Ibs. 

i  part  cement,  3  parts  sand. 

7  days,  (i  day  in  air,  6  days  iu  water) 25  to    75  Ibs. 

28  days,  (i  day  in  air,  27  days  in  water) 75  to  150  Ibs. 

Soundness.  Standard  pats  kept  in  air  and  in  water  should  remain  firm  and 
hard  and  show  no  signs  of  cracking  or  disintegration. 


26  STREET  ROADWA  Y  PA  VEMENTS 

shall  develop  a  tensile  strength  per  square  inch  not  less  than  the 
following : 

In  seven  days 175  pounds. 

In  twenty-eight  days 250  pounds. 

Constancy  of  Volume. — When  subjected  to  standard  tests  for 
constancy  of  volume,  the  cement  shall  show  no  tendency  to  swell 
or  crack. 

Composition. — The  cement  shall  not  contain  more  than  one  and 
three-fourths  (1.75)  per  cent,  of  anhydrous  sulphuric  acid,  nor  more 
than  four  (4)  per  cent,  of  magnesia. 

Tests. — Cement  tests  shall  be  conducted  in  accordance  with  the 
methods  recommended  by  the  "  Committee  on  Unifoim  Tests  of 
Cement"  of  the  American  Society  of  Civil  Engineers. 

Conditions. — All  cement  shall  be  supplied  in  original  packages 
with  the  brand  of  the  manufacturer  marked  on  each  package.  It 
shall  be  protected  during  transportation  from  rain  and  moisture. 
It  shall  be  delivered  upon  the  work  at  least  ten  (10)  days  (exclus- 
ive of  Sundays  and  holidays)  before  it  is  to  be  used,  in  oredr  to 
allow  of  proper  inspection,  and  the  contractor  shall  furnish  all 
necessary  facilities  for  such  inspection.  Brands  of  cement  without 
established  good  reputation,  or  not  heretofore  used  in  the  City  of 

may  be  rejected;  or  they  will  be  accepted 

only  after  they  satisfactorily  pass  the  2$-day  test.  Rejected  cement 
must  be  at  once  removed  from  the  street. 

30.  Sand.— Sand    for  concrete  shall  be  composed  of  grains  not 
softer  than  hard  limestone.     It  shall  be  moderately  coarse  and 
preferably  made  up  of  grains  of  varying  size  producing  a  mass  with 
low  percentage  of  voids.     It  shall  not  contain,  in  all,  more  than 
seven  (7)  per  cent,  by  volume  of  clay,  loam,  mica  scales,  silt,  or  other 
objectionable  inorganic  matter,  nor  more  than  one  (i)  per  cent,  of 
organic  matter. 

31.  Broken  Stone. — Broken  stone  for  concrete  shall  be  of  hard  and 
sound  limestone  or  other  stone  equally  hard  and  durable,  broken  to 
a  roughly  cubical  form.     It  shall  be  screened  through  efficient 
revolving  screens,  and  only  such  fragments  as  have  passed  through 
circular  screen  openings  two  and  one-half  (2  1/2)  inches  in  diameter, 
shall  be  used.     If  the  crushed  dust  and  fine  fragments  be  not 
screened  out,  the  stone  must  be  so  handled  that  the  fine  material 


SPECIFICATIONS  27 

will  be  evenly  distributed  through  the  mass  when  it  reaches  the 
concrete  platform  or  mixer.1 

32.  Water. — Water  used  for  concrete  shall  be  fresh,  and  reason- 
ably clean. 

33.  Care  and  Handling  of  Concrete  Material. — Cement  must 
not  be  allowed  to  become  wet  or  damp.     It  shall  be  stored  until 
used,  whether  in  storehouses  or  on  the  street,  so  that  no  part  of  the 
packages  shall  be  nearer  than  four  (4)  inches  to  the  ground  or  pave- 
ment, and  shall  be  effectually  covered  so  that  rain  cannot  reach  it. 
Sand  and  stone,  if  stored  on  the  street,  shall  be  on  lumber  floors.2 
The  stone  shall  be  thoroughly  wetted  a  sufficient  time  before"  being 
placed  in  the  concrete  to  allow  any  surplus  water  to  drain  away, 
but  shall  remain  moist  where  it  reaches  the  concrete  platform  or 
mixer. 

34.  Ratio  of  Concrete  Materials. — Concrete  will  be  composed  of 

one  part  Portland  cement parts  of  sand  and 

parts  of  broken  stone,  and  the  proper  quantity 

of  water,  all  measured  by  volume.3     The  unit  of  measurement  shall 

1  The  frequent  requirement  that  the  fine  material  shall  be  screened  out,  is  not 
necessary  or  advisable.     Experiments  and  experience  have  shown  conclusively 
that  unless  an  unusual  amount  of  fine  material  and  "dust"  be  present,  or  unless 
this  fine  material  be  allowed  to  separate  and  aggregate  in  masses  by  itself,  the 
resulting  concrete  is  improved  rather  than  deteriorated  by  its  presence. 

Where  there  is  an  unusual  excess  of  "dust"  in  the  crushed  stone,  the  quantity 
of  sand  used  in  the  concrete  should  be  decreased  accordingly. 

2  Many  specifications  do  not  require  this  and  in  a  number  of  cities  where  the 
specifications  do  require  it,  contractors  habitually  neglect  to  comply.     When 
stone  and  sand  are  deposited  directly  upon  the  earth,  it  is  very  difficult  to  avoid 
taking  up  earth  and  mud  with  the  materials,  particularly  when  the  street  is  wet 
and  muddy.    Lumps  of  soil  and  debris  unquestionably  injure  the  concrete.     The 
cost  of  providing  a  lumber  floor  is  comparatively  small,  as  the  plank  may  be 
used  over  and  over  again.     Specifications  should,  therefore,  contain  this  require- 
ment and  it  should  be  enforced. 

3  The  ratios  of  the  materials  may  appropriately  be  varied  with  the  strength 
and  soundness  of  the  sub-foundation,  the  amount  of  travel  on  the  street,  and 
with  the  thickness  of  foundation  it  is  proposed  to  use.     Where  good  materials 
are  used  and  the  work  is  properly  done,  a  i  :  3  : 5  concrete  six  inches  thick  is  suffi- 
cient for  streets  of  the  heaviest  travel.     For  streets  of  light  travel  a  i  :  5  : 9  concrete 
will  usually  give  entirely  satisfactory  results.     The  most  economical  thickness 
for  a  concrete  foundation  is  an  important  consideration.     The  strength  of  con- 
crete may  be  said  to  increase,  within  usual  limits  of  practice,  with  the  ratio  of 
cement  in  it.     The  strength  of  concrete  beams  or  slabs  increases  in  the  ratio  of  the 
square  of  their  depth.     To  secure  a  required  amount  of  strength  in  a  pavement 
foundation,  we  may  therefore  vary  the  richness  of  the  concrete  and  the  depth 
of  the  foundation  so  as  to  secure  the  requisite  strength  at  the  least  total  cost  of 


28  STREET  ROA DWA  Y  PA  VEMENTS 

be  the  barrel  of  cement  which  shall  be  considered  as  containing  four 
(4)  cubic  feet.  The  materials  shall  each  be  measured  in  such  manner 
and  with  such  accuracy  that  the  quantities  used  will  not  vary  more 
than  seven  (7)  per  cent,  from  the  quantities  required  in  the  ratio 
named  above  for  each  batch  of  concrete 

35.  Mixing  Concrete. — If  mixed  by  hand,  concrete  shall  be  mixed 
on  platforms  of  iron  or  wood  of  sufficient  size  to  admit  of  proper 
manipulation  of  the  concrete.  The  sand  shall  be  first  spread  evenly 
over  the  platform  and  the  cement  evenly  distributed  over  the  sand. 
These  two  materials  shall  then  be  mixed  dry  until  a  uniform  and 
homogeneous  mixture  is  secured.  Sufficient  water  shall  then  be 
added  and  the  mixing  resumed  and  continued  until  a  mortar  of 
uniform  consistency  and  texture  is  produced  and  distributed  in  an 
even  layer  over  the  platform.  The  stone  shall  then  be  distributed 
over  the  mortar  and  mixed  therewith  until  the  mortar  is  evenly 
distributed  through  the  mass  and  every  fragment  of  stone  is  well 
coated  with  mortar,  sufficient  additional  water  being  added  as 
the  mixing  progresses  to  produce  a  rather  wet,  but  not  sloppy, 
concrete.1  Machine  mixing  of  concrete  will  be  preferred,  provided 

materials  and  labor.  This  will  be  influenced  by  the  cost  of  materials  and  labor 
in  each  particular  locality. 

Within  certain  workable  limits  there  is  no  reason  why  the  same  principles  of 
proportioning  the  strength  of  a  pavement  foundation  to  the  work  required  of  it 
should  not  be  applied  as  are  employed  in  designing  other  engineering  structures. 

The  practice,  usual  in  many  cities,  of  adopting  general  specifications  requiring 
a  standard  thickness  of  foundation  and  composition  of  concrete,  and  applying 
these  to  all  streets,  regardless  of  the  quantity  and  character  of  travel  which 
the  pavement  is  expected  to  carry,  is  illogical  and  often  very  wasteful.  If 
such  a  standard  foundation  is  sufficient  for  the  streets  of  heaviest  travel,  it  is 
obviously  a  sheer  waste  of  money  to  use  it  on  the  suburban  streets  carrying  the 
lightest  travel.  It  is  therefore  better  in  preparing  standard  specifications  for 
pavement  in  any  city  to  leave  blanks  for  the  ratios  of  the  concrete  and  for  the 
thickness  of  the  foundation,  to  be  filled  in,  in  each  individual  case,  as  the  judg- 
ment of  the  engineer  may  dictate. 

While  it  is  important  that  the  foundation  of  any  pavement  shall  be  adequate, 
it  is  inexcusable  to  waste  money  in  providing  superfluous  strength.  For  the 
great  majority  of  suburban  streets,  carrying  but  little  except  the  local  travel,  a 
foundation  four  inches  thick  made  of  good  Portland  cement  concrete  in  the 
ratios  of  i  :  4  : 8  will  prove  entirely  satisfactory.  Hundreds  of  such  streets  paved 
over  a  foundation  of  that  thickness,  made  of  natural  cement  concrete  in  the 
ratios  of  i  :  2  : 4  can  be  cited  where  the  foundation  has  proved  entirely  satisfactory. 

The  character  and  firmness  of  the  sub-foundation  must,  of  course,  be  taken 
into  consideration  in  designing  the  foundation. 

1  The  routine  here  described  produces  better  concrete  with  less  expenditure  of 
labor,  than  the  one  often  followed  of  putting  all  the  dry  materials  on  the  concrete 


SPECIFICATIONS  29 

the  machine  used  secures  equal  accuracy  in  the  ratios  of  materials 
and  equally  as  good  mixing  as  prescribed  above  for  hand-mixing. 
Machine-mixed  concrete  must  be  delivered  from  the  machine  upon 
a  wood  or  metal  platform,  or  directly  into  barrows. 

36.  Placing  the  Concrete. — Concrete  shall  be  placed  on  the  sub- 
grade  in  such  a  manner  as  to  prevent  as  far  as  possible  the  separation 
of  the  mortar  from  the  stone.     It  shall  be  evenly  distributed  in  a 
single  horizontal  layer  of  such  depth  that,  after  ramming,  it  will  be 

not  less  than inches  thick.      Immediately  after  being 

so  placed  it  shall  be  well  rammed  until  a  compact  mass  is  pro- 
duced with  its  upper  surface  parallel  to  and inches 

below    the    pavement    datum.       Depressions    that    may    appear 
during   the   ramming   may   be   filled  with   concrete   of   the   same 
composition   as   used   for    the    foundation,    except    that    smaller- 
sized  stone  shall  be  used;  mortar  alone  must  not  be  used  for  this 
purpose,  nor  shall  the  upper  surface  of  the  concrete  be  plastered 
with  mortar.     The  surface  of  the  concrete  shall  not  be  broomed  or 
'troweled.1 

37.  Setting  of  Concrete. — After  the   concrete  is  completed  it 
shall  remain  undisturbed  until  it  be  firmly  set.     The  time  allowed 
for  setting  shall  not  be  less  than  five  days,  and  as  much  longer  as, 
in  the  judgment  of  the  Engineer,  may  be  necessary,  depending 
upon  the  temperature  of  the  weather  and  the  setting  qualities  of 
the  cement.     During  this  period  no  hauling  or  traveling  over  the 
concrete  must  be  permitted  unless  its  surface  be  first  protected  by 
a  covering  of  plank.     The  Contractor  shall,  if  necessary,  keep  the 
concrete    moist    by    wetting    it,    with    hose,    or    otherwise,    until 
twenty-four  (24)  hours  before  it  is  to  be  covered  with  the  pavement 
surface. 

38.  Measurement  of  Concrete. — Concrete  will  be  measured  and 
computed  in  cubic  yards  as  found  completed  on  the  street,  the  thick- 
board  before  any  mixing  is  begun.     The  writer  has  proved  this  from  actual 
records  covering  a  large  quantity  of  work. 

1  The  objections  to  using  mortar  for  plastering  over  the  concrete  are:  that  it 
is  more  costly  than  concrete;  that  the  two  materials  may,  under  certain  condi- 
tions, separate  and  the  thin  mortar  surface  break  up  under  travel;  that,  if  per- 
mitted, the  mortar  may  be  used  to  cover  up  defective  concrete,  and  that  in  the 
case  of  asphalt  pavements  the  pavement  surface  is  more  likely  to  "shift"  on  the 
smooth  surface  of  the  mortar  than  on  the  rough  surface  of  the  concrete.  The 
practice  of  going  over  the  fresh  concrete  with  street  brooms  should  not  be  per- 
mitted. The  only  argument  in  favor  of  it  is  that  it  may  be  used  to  conceal 
defective  patches  in  the  concrete. 


30  STREET  ROADWAY  PAVEMENTS 

ness  being  taken  as inches.     The  contract  price 

for  concrete  foundation  covers  the  cost  of  providing  all  the  materials 
required,  making,  placing  and  ramming  the  concrete,  and  keeping 
it  moist  for  the  necessary  period. 

FOUNDATION  OF  OLD  PAVING  STONE 

39.  Foundations  made  of  old  stone  paving  blocks  shall  be  con- 
structed as  follows: 

Upon  the  sub-grade  prepared  as  specified  in  Section  26,  shall  be 
spread  a  layer  of  good  sand  to  an  eveln  depth  of  one  and  one-half 
(i  i/  2)  inches.  The  paving  blocks,  whether  taken  up  from  the  street 
to  be  paved,  or  brought  from  other  streets  or  storage  yards,  shall 
be  cleaned  of  all  adhering  earth,  dirt  and  street  refuse.  The  blocks 
shall  then  be  set  on  the  bed  of  sand,  on  edge,  perpendicular  to 
the  grade,  with  their  long  dimension  at  right  angles  to  the  line  of  the 
street,  in  courses  composed  of  stones  of  the  same  width,  extending 
entirely  across  and  at  right  angles  to  the  axis  of  the  street.  Stones 
in  adjoining  courses  shall  break  joint  at  least  two  inches.  Joints 
between  courses  or  stones,  or  along  the  curbstones,  shall  not  exceed 
one  inch  in  width.  The  stone  shall  be  fitted  closely  around  man- 
holes or  other  structures  in  the  street.  The  stones  shall  be  so  set 
in  the  bed  of  sand  that  after  being  rammed  as  hereafter  specified, 
their  tops  shall  be  at  the  proper  grade.  After  being  thus  set  in 
place  the  stone  shall  be  rammed  with  paving  rammers  having 
wooden  faces  and  weighing  not  less  than  thirty  (30)  pounds,  so  as 
to  force  each  stone  to  a  good  bearing  in  the  sand  below,  and  to 

bring  its  top  to  a  uniform  grade,  parallel  to  and 

inches  below  the  pavement  datum.  No  stone  shall  project  more 
than  one-fourth  (1/4)  inch  above  the  proper  grade,  and  stones 
whose  tops,  after  ramming,  are  more  than  one-half  (1/2)  inch  below 
such  grade,  shall  be  raised,  additional  sand  placed  under  them,  and 
reset  and  re-rammed  to  the  proper  grade  and  bearing.  After  the 
ramming  shall  have  been  completed,  the  joints  between  the  stones 
shall  be  filled  with  mortar.  The  mortar  shall  be  composed  of  Port- 
land cement  and  sand,  complying  with  the  specifications  for  these 
materials  in  Sections  29  and  30.  One  part  of  cement  and  three 
parts  of  sand,  by  volume,  shall  be  thoroughly  mixed  dry,  and  then 
made  into  mortar  with  sufficient  quantity  of  water  to  produce  a 
mortar  of  such  consistency  that  it  will  just  flow  freely  into  the  joints 
between  the  stones.  All  the  joints  between  the  stones  must  be 


SPECIFICATIONS  31 

completely  filled  with  this  mortar  before  it  has  begun  to  set.  The 
mortar  filling  shall  be  brought  even  with,  but  not  above,  the  tops 
of  the  stones.  After  the  filling  is  thus  completed,  the  foundation 
must  stand  undisturbed  until  the  mortar  shall  have  set  firmly,  in 
no  case  less  than  five  days.  The  mortar  must  be  kept  moist  during 
the  period  allowed  for  setting.1 

Old  stone  foundation  will  be  measured  in  square  yards,  in  place 
after  completion.  The  contract  price  includes  the  cost  of  handling 
and  cleaning  the  stone,  supplying  and  placing  the  bed  of  sand,  setting 
and  ramming  the  stone,  supplying  the  materials  for,  making  and 
placing  the  mortar  in  the  joints  and  watering  the  street  while  the 
mortar  is  setting.  Where  stone  is  procured  from  other  streets,  or 
from  storage  yards,  the  Contractor  will  be  required  to  load,  haul 
and  unload  them,  and  will  be  allowed  for  this  service  a  price  of 

cents  per  cubic  yard  for  loading  and  unloading,  plus 

cents  per  cubic  yard  for  each  one-half  mile,  or  fraction  thereof,  over 
which  they  are  hauled  by  the  nearest  practicable  route,  the  meas- 
urement to  be  made  after  the  stone  is  set  in  the  street,  without 
deduction  for  joints. 

40.  Broken-stone  Foundation. — The  sub-grade  for  broken-stone 
foundation  shall  be  prepared  as  specified  in  Section  26,  except  that 

1  See  foot-note,  p.  23.  The  cost  of  filling  the  joints  of  old  block  pavement 
with  mortar  or  grout  is  considerable.  It  will  hardly  ever  be  less  than  20  cents 
and  may  exceed  35  cents  per  square  yard,  depending  on  the  volume  of  joints 
and  the  local  cost  of  material  and  labor.  The  cost  of  resetting  and  ramming 
the  blocks  with  proper  care  will  usually  be  from  10  cents  to  12  cents  per  square 
yard,  so  that  the  cost  of  the  foundation,  exclusive  of  the  value  of  the  blocks,  may 
vary  from  30  cents  to  47  cents  per  square  yard. 

As  a  good  concrete  foundation  6  inches  in  depth  can  be  laid  for  from  70  to  90 
cents  per  square  yard,  it  is  obvious  that  if  the  old  blocks  can  be  sold  for  as  much 
as  the  difference  between  the  cost  of  the  old  block  and  the  concrete  foundation, 
nothing  will  be  saved  by  using  the  old  block  foundation.  In  at  least  one  city, 
asphalt  pavement  has  been  extensively  laid  over  old  stone  block  foundation 
relaid  in  a  very  careless  manner,  the  joints  being  filled  usually  with  the  old  sand 
or  loam  found  in  the  street.  This  practice  cannot  be  too  strongly  condemned. 
Asphalt  pavement  surfaces  resting  on  such  a  foundation  are  necessarily  short- 
lived and  unsatisfactory.  The  practice  of  opening  the  street  to  travel  for  a 
period  after  the  blocks  are  relaid  and  before  the  asphalt  surface  is  applied,  helps, 
under  favorable  conditions,  to  consolidate  the  foundation,  but  does  not  remove 
the  objections  to  it.  If  heavy  rains  intervene,  the  sub-foundation  becomes 
saturated  with  water,  and  its  resistance  so  reduced  that  the  stone  blocks  settle 
out  of  shape,  particularly  in  soft  spots,  and  they  are  usually  hastily  raised  and 
reset  just  before  the  asphalt  surface  is  applied.  The  result  is  an  insecure  founda- 
tion fatal  to  the  durability  and  usefulness  of  the  pavement. 


32  STREET  ROADWA  Y  PA  VEMENTS 

the  rolling  may  be  omitted  at  the  option  of  the  Contractor.  The 
broken  or  crushed  stone  shall  be  of  hard,  durable  stone.  The 

foundation  shall  have  an  aggregate  thickness  of inches  and 

shall  be  constructed  in  two  courses,  as  follows: 

The  broken  stone  used  in  the  first  course  shall  be  of  such  size 
that  it  will  all  pass  through  a  screen  having  openings  three  (3) 
inches  in  diameter,  and  will  all  be  retained  on  a  screen  having 
openings  one  (i)  inch  in  diameter.  This  stone  shall  be  evenly 
spread  over  the  sub-grade  to  such  a  thickness  that  after  being 
thoroughly  consolidated  by  rolling,  its  upper  surface  shall  be  three- 
fourths  inch  below,  and  parallel  to  the  surface  of  the  foundation 
when  completed.  It  shall  then  be  rolled  with  a  road-roller  weighing 
not  less  than  ten  (10)  tons  until  the  stone  is  thoroughly  compacted. 

The  second  course,  composed  of  screenings,  all  of  which  shall 
have  passed  through  a  screen  with  openings  one  inch  in  diameter, 
shall  then  be  spread  over  the  first  course  and  well  raked  into  the 
voids  of  the  first  course.  It  shall  then  be  thoroughly  wetted,  and 
shall  be  rolled  with  the  ten- ton  roller  until  the  fine  stone  is  driven 
into  the  interstices  of  the  first  course  and  the  whole  thoroughly 
consolidated,  the  wetting  being  repeated  while  the  rolling  continues. 
Additional  screenings  shall  be  added  and  rolled  in  where  necessary 
to  bring  the  surface  to  the  proper  elevation.  When  completed,  the 

top  surface  of  the  foundation  shall  be inches  below, 

and  parallel  to  the  pavement  datum.  No  part  of  the  upper  surface 
of  the  completed  foundation  shall  project  more  than  one-fourth  (1/4) 
inch  above,  nor  shall  it  be  more  than  one-half  (1/2)  inch  below  the 
grade  and  contour  above  specified. 

Gravel  of  a  quality  satisfactory  to  the  Engineer  may  with  his 
written  consent  be  substituted  for  broken  stone.  If  of  assorted 
sizes,  such  as  will  compress  into  a  mass  having  not  more  than  thirty 
(30)  per  cent,  of  voids,  the  foundation  may  be  constructed  in  a 
single  layer,  graded,  watered  and  rolled,  as  prescribed  above  for 
broken  stone.1 

41.  Measurement. — Broken-stone  and  gravel  foundation  will  be 
measured  and  computed  by  the  cubic  yard  in  the  street  as  completed, 
without  any  allowance  for  consolidation  by  the  roller  or  for  settle- 
ment into  the  sub-grade,  the  thickness  being  taken  as 

1  Where  there  is  a  possibility  that  gravel  may  be  used,  the  contractor  should 
be  asked  to  name  prices  for  the  gravel  foundation  as  well  as  the  stone  foundation, 
since,  unless  this  be  done,  the  change  from  the  one  material  to  the  other  might 
be  held  to  be  illegal. 


SHEET  ASPHALT  PAVEMENT 


33 


inches.     The  contract  price  for  it  shall  cover  the  cost  of 

supplying  the   material,   placing   it   on   the  street,   and  grading, 
watering  and  rolling  it. 


SHEET  ASPHALT  PAVEMENT 

Note. — A  number  of  distinct  varieties  of  asphalt  are  now  used  for 
asphalt  pavements,  either  alone  or  mixed.  These  different  varieties  differ 
from  each  other  quite  widely  in  their  physical  and  chemical  properties. 
Thus,  in  the  form  called  "refined  asphalt"  some  of  their  properties  are 
shown  by  the  following  table,  the  data  for  which  is  taken  from  the  second 
edition  of  Richardson's  "The  Modern  Asphalt  Pavement." 

COMPARATIVE  PROPERTIES  OF  DIFFERENT  REFINED  ASPHALTS 


Trinidad, 
average 

Bermudez, 
average 
of  two 
samples 

Mara- 
caibo, 
average 
of  six 
samples 

Calif. 
"D"  grade, 
average 
of  two 
samples 

Gilsonite, 
average 
of  two 
samples 

Softens,  degrees  F.  . 

180 

165 

225 

.132 

280 

Flows,  degrees  F..  . 

190 

175 

236 

151 

300 

Penetration  at  78°  F. 

7 

24 

21 

48 

0 

Loss,  heated  to  3  25° 

for  7  hours,  %. 

1.  1 

3-7 

3-2 

i-7 

1.6 

Loss,  heated  to  400° 

for  7  hours,  %. 

4.0 

8.8 

5-5 

7-i 

2.6 

Bitumen  soluble  in 

CS2. 

56.5 

95-5 

93-9 

99-3 

99-4 

Inorganic,    other 

than  bitumen. 

36.5 

2.  2 

2.9 

o-3 

o-5     • 

Bitumen  soluble  in 

naphtha. 

35-6 

65-6 

SLI 

69.6 

47-2 

Bitumen  sol.  in  car- 

bon  tetrachloride. 

98.7 

99.0 

93-2 

95-7 

99-8 

Fixed  carbon  

10.8 

13-7 

17.2 

17.6 

13.2 

The  practice  has  been  heretofore,  and  is  at  the  present  time,  to  attempt 
to  make  specifications  for  asphalt  pavements  broad  enough  to  include  all 


34  STREET  ROA DWA  Y  PA  VEMENTS 

the  various  varieties  of  asphalts,  under  general  requirements  which  shall 
admit  these,  and  any  new  varieties  that  may  appear  on  the  market 
suitable  for  the  purpose,  the  object  being  to  permit  a  wide  range  of  com- 
petition. This  makes  it  exceedingly  difficult  if  not  impossible  to  frame 
specifications  that  shall  be  sufficiently  explicit  and  at  the  same  time 
sufficiently  broad  to  admit  these  several  differing  materials.  This  practice 
has  been  adhered  to  in  these  specifications,  though  in  this  respect  they  are 
far  from  satisfactory  to  the  author.  So  long  as  it  continues  to  be  the  policy 
of  cities  to  admit  these  various  varieties 'of  bitumen  under  the  same 
general  requirements  for  crude  and  refined  material,  such  objectionable 
specifications  cannot  be  avoided.  Even  with  the  great  latitude  now 
provided  they  exclude  some  materials  with  which  good  pavements  have 
been  made. 

Two  remedies  for  this  unsatisfactory  condition  seem  practicable. 

1.  A  city  might  purchase  a  sufficient  supply  of  refined  asphalt  for  its 
use  after  asking  for  proposals  under  suitable  specifications  with  alternative 
requirements  for  the  different  varieties  on  the  market,  and  after  bids  are 
received  and  the  samples  accompanying  them  have  been  properly  ex- 
amined in  the  laboratory,  award  contracts  for  a  supply  of  one  or  more 
kinds,  as  might  seem  best  for  the  interests  of  the  city.     Stocks  of  these 
would  be  delivered,  tested  and  stored  accordingly,  in  good  time  for  the 
season's  work.     Specifications  for  construction  with  special  reference  to  the 
kind  of  asphalt  it  is  proposed  to  use  could  then  be  prepared,  the  con- 
tractors to  be  supplied  with  asphalt  at  the  city  storage  yard  at  a  stipulated 
price  per  ton.     This  plan  would  possess  a  number  of   advantages.     A 
similar  plan  is  quite  commonly  in  use  with  reference  to  hydraulic  cement. 

2.  Specifications  might  be  framed  with  special  reference  to  the  properties 
and  qualities  to  be  possessed  by  the  asphaltic  cement,  permitting  a  liberal 
range  as  to  the  crude  and  refined  bitumens  to  be  used  in  manufacturing 
this  cement.     This  would  be  considered,  at  the  present  time,  a  radical 
departure  from  well  established  custom,  but  the  author  sees  no  reason 
why  it  should  not  be  satisfactorily  employed. 

A  sheet  asphalt  pavement  is  composed  of  two  essential  elements;  a 
mineral  aggregate  made  up  of  sand  of  assorted  sizes  and  mineral  "dust" 
and  a  bituminous  cement.  When  properly  compounded,  manipulated 
and  compressed  these  elements  make  up  a  bituminous  concrete  suitable 
for  use  as  a  wearing  surface  for  streets  and  roads. 

The  character  of  the  sand  is  important  and  we  have  now  sufficient 
knowledge  from  experience  to  specify  a  sand  that  will  give,  approximately, 
the  best  results. 

The  bituminous  cement  is,  however,  the  element  of  most  importance, 
and  upon  its  suitability  for  the  purpose  depends  very  largely  the  utility 
and  durability  of  the  pavements  made  with  it. 

It  is  important  that  this  asphaltic  cement  shall  possess  certain  properties 
and  qualities,  most  of  which  we  are  now  able  to  define  satisfactorily,  but 


SHEET  ASPHALT  PAVEMENT  35 

others  require  further  practical  and  experimental  study,  and  some  tests 
not  now  in  use  would  doubtless  be  desirable. 

It  is  not  a  matter  of  importance  what  particular  crude  or  refined 
materials  enter  into  the  composition  of  this  cement  if  the  resulting  product 
is  satisfactory  in  use.  The  prime  requisite  is  a  paving  cement  that  shall 
possess  in  a  high  degree  the  chemical  and  physical  qualities  required  for 
making  an  asphalt  pavement  of  the  best  quality.  If  we  can  devise 
standards  and  tests  that  will  enable  us  to  secure  such  a  cement  we  need  not 
be  concerned  about  its  antecedents. 

It  would  be  well  worth  while  for  paving  engineers  and  those  who  have 
laboratory  facilities  to  give  attention  to  this  matter.  If  it  shall  be  found 
practicable  to  define  satisfactorily  the  qualities  the  cement  should  possess 
without  reference  to  the  materials  from  which  it  is  compounded,  a  great 
advance  will  have  been  made,  and  our  asphalt  paving  specifications 
could  not  only  be  greatly  simplified,  but  much  greater  precision  and  defi- 
niteness  secured. 

While  great  advances  have  been  made  in  the  art  of  building  sheet 
asphalt  pavements  and  in  the  framing  of  specifications  for  its  construction, 
too  many  of  the  specifications  still  in  use  are  antiquated,  indefinite  and 
unsatisfactory.  Some  of  these  contain  requirements  that,  if  literally 
enforced,  would  prevent  the  attainment  of  the  best  results.  They  are 
largely  survivals  of  the  time  when  little  was  known  either  practically  or 
technically  of  the  science  and  art  of  constructing  the  pavements,  outside 
of  the  promoters  and  contractors  in  the  business,  who  consequently 
dictated,  in  a  large  measure,  the  specifications  used.  City  engineers  were 
compelled  to  rely  largely  on  the  presumption  that  the  guarantee  clauses 
of  the  contracts  would  insure  good  results,  and  allowed  the  contractor 
wide  latitude  in  the  conduct  of  the  work. 

While  there  is  undoubtedly  much  yet  to  learn,  even  by  the  experts,  in 
the  matter  of  the  materials  to  be  used,  a  quite  satisfactory  working  basis 
has  been  arrived  at,  particularly  as  to  the  practical  side  of  the  work,  and 
a  large  mass  of  data  accumulated  by  study  and  experience  is  available  to 
the  municipal  engineer,  and  the  services  of  independent  experts  is  readily 
obtainable.  There  is  no  longer  any  good  reason,  therefoie,  why  the 
character  of  the  materials  to  be  used,  the  methods  followed,  and  the  quality 
of  the  work  secured  should  not  be  quite  definitely  and  fully  specified  in 
the  same  manner  and  to  the  same  extent  as  in  the  case  of  other  kinds  of 
pavement  and  with  equally  satisfactory  results. 

SPECIFICATIONS 

42.  General. — Asphalt  pavement  surface  shall  be  laid  upon  a 
foundation  of  hydraulic  cement  concrete,  or  of  stone  blocks  relaid, 
over  a  sub-grade,  to  be  constructed  in  accordance  with  Articles  26, 
28,  29,  30,  31,  32,  33,  34,  35,  36  and  37. 


36  STREET  ROADWA  Y  PA  VEMENTS 

Asphalt  pavement  surface  shall  be  constructed  in  two  courses, 
called  the  base-course  and  the  surface-course.  The  base-course  may 
be  from  one  (i)  inch  to  one  and  one-half  (i  1/2)  inches  thick,  and 
the  surface-course  may  be  from  one  (i)  inch  to  two  (2)  inches  thick, 
as  shall  be  hereafter  specified. 

43.  Crude  Asphalt. — The  cementing  element  in  asphalt  pavements 
shall  be  prepared  from  crude  native,  solid  asphalts  or  from  the 
proper  distillation  of  crude  asphaltic  oils. 

Crude  asphalts  as  obtained  from  the  mines  or  natural  deposits 
shall  be  properly  refined  to  drive  off  water  and  to  separate  foreign 
substances,  by  melting  at  a  temperature  not  exceeding  four  hundred 
and  fifty  degrees  F.  (450°  F.).  Crude  asphalts  of  the  quality 
commonly  called  "glance  pitch"  or  "iron  pitch"  which  do  not 
distinctly  soften  at  a  temperature  of  two  hundred  degrees  F.  (200° 
F.),  and  detached  or  deteriorated  material  from  deposits  otherwise 
acceptable  will  be  rejected. 

44.  Refined   Asphalt. — Refined   asphalt   produced  from   native 
crude  asphalt  shall  be  free  from  water  and  shall  not  contain  an  in- 
jurious quantity  of  light  oils  or  foreign  matter.     It  shall  not  contain 
more  than  four  per  cent.  (4%)  of  organic  matter  nor  more  than  thirty- 
six  per  cent.  (36%)  of  inorganic  matter  other  than  bitumen,  and  not 
moie  than  eighteen  per  cent.  (18%)  of  fixed  carbon,  and  not  less  than 
fifty-five  per  cent.  (55%)  of  bitumen  soluble  in  cold  carbon  disul- 
phide.     Of  the  bitumen  soluble  in  carbon  di-sulphide  not  less  than 
sixty- three  per  cent.  (63%)  shall  be  soluble  in  Pennsylvania  petro- 
leum naphtha  of  specific  gravity  eighty-eight  (88)  degrees  Baume  at  a 
temperature  of  sixty-five  degrees  Fahrenheit  (65°  F.)  and  not  less 
than  ninety-eight  per  cent.  (98%)  shall  be  soluble  in  chemically  pure 
carbon  tetra-chloride.     When  exposed  for  seven  hours  to  a  tempera- 
ture of  three  hundred  and  twenty-five  degrees  F.  (325°  F.)  in  a  shallow 
dish  the  bottom  of  which  is  covered  with  bitumen  to  a  depth  of 
three-fourths  (3/4)  inch,  the  refined  asphalt  shall  not  lose  more  than 
five  per  cent.  (5%)  by  evaporation. 

Asphalts  that  are  injuriously  affected,  in  the  pavement,  by  water 
(to  be  determined  by  the  test  immediately  hereinafter  described), 
shall  not  be  used  except  under  the  conditions  specified  in  Section  45. 
Cylinders  made  from  the  surface  mixture  it  is  proposed  to  use,  one 
(i)  inch  in  diameter  and  two  (2)  inches  long,  compressed  to  a 
density  of  two  and  one-tenth  (2.1),  when  immersed  forty -five 
(45)  days  in- ten  (10)  times  their  volume  of  rain-water,  shall  retain  a 
sound  surface,  unchanged  and  uncorroded  by  the  action  of  the  water. 


SHEET  ASPHALT  PA  VEMENT  37 

Refined  asphalts  resulting  from  the  distillation  of  crude  asphaltic 
oils  will  not  be  accepted  unless  the  distillation  shall  have  been  effected 
by  the  use  of  suitable  apparatus,  at  a  temperature  not  exceeding 
seven  hundred  (700)  degrees  F.  The  bitumen  must  not  be  over- 
distilled  and  "cut  back"  by  adding  oil.  The  product,  to  be  accept- 
able, shall  possess  the  following  qualities :  It  shall  melt  and  flow  at 
a  temperature  not  below  one  hundred  and  forty  (140)  degrees  F.,  but 
below  a  temperature  of  one  hundred  and  eighty  (180)  degrees  F., 
and  when  tested  in  the  standard  New  York  State  closed  oil-testing 
apparatus  shall  not  flash  at  a  temperature  below  four  hundred  and 
fifty  (450)  degrees  F.  When  exposed  in  a  shallow  dish,  the  bottom 
of  which  is  covered  to  a  depth  of  three-fourths  (3/4)  inch  with  the 
bitumen,  to  a  temperature  of  four  hundred  (400)  degrees  F.,  for 
seven  (7)  hours,  it  shall  not  lose  by  evaporation  more  than  seven  (7) 
per  cent,  by  weight.  Not  less  than  ninety-eight  (98)  per  cent,  shall 
be  soluble  in  cold  carbon  di-sulphide,  and  not  less  than  sixty-five 
(65)  per  cent.,  nor  more  than  seventy-five  (75)  per  cent,  of  the 
bitumen  shall  be  soluble  in  cold  Pennsylvania  naphtha  of  gravity 
eighty-eight  (88)  degrees  Baume.  Not  less  than  ninety-nine  (99) 
per  cent,  of  the  bitumen  shall  be  soluble  in  carbon  tetra-chloride, 
and  it  shall  not  contain  more  than  sixteen  (16)  per  cent,  of  fixed 
carbon.1 

Bitumens  resulting  from  destructive  distillation  or  from  arti- 
ficial oxidation,  and  bituminous  compounds  prepared  from  oil  or  oil 
residuums  heated  with  sulphur  or  other  substances,  or  coal  or  gas 

1  There  has  been  much  discussion  as  to  the  suitableness  of  these  oil  asphalts, 
called  "residual  pitches,"  for  use  in  making  asphalt  pavements.  When  properly 
prepared  from  suitable  asphaltic  oils,  so  as  to  comply  with  the  specifications 
here  given,  there  can  be  no  doubt  that  good  pavements  can  be  made  with  them. 
But  as  they  appear  on  the  market,  being  usually  produced  at  different  localities 
and  refineries  from  crude  oils  of  differing  qualities,  distilled  by  somewhat  differing 
methods,  and  usually  at  temperatures  of  from  900  degrees  to  1200  degrees,  they 
are  likely  to  vary  so  greatly  in  quality  as  to  make  their  use  inadvisable  without 
careful  technical  inspection.  Unless,  therefore,  the  engineer  is  prepared  to  make, 
or  to  have  such  inspection  made,  it  is  hardly  wise  or  safe  to  permit  their  use. 
They  stand,  in  this  respect,  upon  a  footing  different  from  the  better-known 
natural  asphalts  obtained  from  large  deposits  of  practically  uniform  character 
and  quality,  where  the  simpler  process  of  refining  is  less  likely  to  effect  injuriously 
the  chemical  quality  of  the  material. 

It  may  be  confidently  predicted  that  any  of  these  "residual  pitches"  which 
comply  with  these  specifications  will,  if  properly  handled,  make  a  good 
pavement. 


38  STREET  ROA  DWA  Y  PA  VEMENTS 

tars,  will  not  be  accepted,  nor  shall  they  be  mixed  with  the  asphalt 
used.1 

45.  Asphalts  that  are  injuriously  affected  by  water,  and  those 
whose  practical  value  for  making  pavements  has  not  been  estab- 
lished, in  the  judgment  of  the  City,  by  sufficient  experience,  will  not 
be  accepted  except  under  such  special  bond  and  guaranty  provisions 
as  the  City  may  prescribe.2 

46.  Full  information  as  to  the  source  and  character  of  the  crude 
asphalt  and  the  method  of  refining  it  shall  be  furnished  to  the 
Engineer  and  verified  by  such  evidence  as  he  may  require. 

47.  Softening  or  Tempering  Agent. — For  softening  and  tempering 
refined  asphalt,  petroleum  residuum  oil  or  liquid  asphalt  shall  be 
used.     It  shall  be  free  from  water,  coke,  and  other  impurities.     Its 
specific  gravity  shall  not  be  below  0.92,  nor  above  1.04.     Its  flash 
test  (determined  in  the  standard  New  York  State  closed  oil-testing 
apparatus)  shall  not  be  under  three  hundred  and  fifty  (350)  degrees 
F.,  and  when  exposed  for  seven  (7)  hours  to  a  temperature  of  three 
hundred  and  twenty-five  (325)  degrees  F.,  in  a  shallow  open  dish, 
the  bottom  of  which  is  covered  by  the  oil  to  a  depth  of  three-fourths 
(3/4)  inch,  it  shall   not    lose   more   than   five    (5)   per   cent,   by 
evaporation.     It  shall  not  contain  more  than  ten  (10)  per  cent,  of 
paraffine  scale. 

48.  Sand. — A  superior  quality  of  sand  will  be  required  and  this 
must  be  secured,  if  necessary,  by  the  admixture  of  two  or  more  sands. 
The  sand  shall  be  silicious  and  so  free  from  organic  matter,  mica, 
soft  grains,  and  other  impurities,  that  these  shall  not  aggregate 
more  than  two  (2)  per  cent,  of  the  mass.     The  grains  shall,  pre- 
ferably, be  moderately  "  sharp"  or  angular,  and  must  be  of  assorted 
sizes  so  that  the  voids  in  the  compacted  mass  of  dry  sand  shall  not 

1  The  possibility  that  some  of  these  compounds  or  artificial  asphalts,  may  be 
suitable  for  use  in  pavements  is  not  denied.     But  in  the  absence  of  a  fuller  knowl- 
edge of  them  than  we  now  have,  and  in  the  light  of  present  experience,  the  only 
safe  course  is  to  reject  them. 

2  It  is  not  intended  here  to  enter  into  an  extended  discussion  of  the  fact  that 
some  asphalts  are  injuriously  affected  by  water,  and  the  bearing  which  this  fact 
should  have  upon  the  selection  of  an  asphalt  for  pavement  purposes.     There 
can  be  no  doubt  that  modern  treatment  and  methods  of  construction  have 
tended  to-  diminish  but  not  wholly  to  prevent  the  disintegrating  effect  of  water 
upon  pavements  made  with  such  asphalt,  and  if  the  engineer  could  be  certain 
that  his  pavements  would  be  constructed  by  contractors  guided  by  long  experi- 
ence and  the  best  expert  advice,  he  might  perhaps  safely  disregard  this  pro- 
vision.    Since  in  practice  he  can  have  no  such  assurance,  the  provision  is  a  wise 
one  and  it  does  not  involve  any  serious  or  material  hardship  to  the  contractor. 


SHEET  ASPHALT  PAVEMENT  39 

exceed  thirty  three  (33)  per  cent.  A  typical  sand,  to  be  approxi- 
mated as  closely  as  practicable,  will  give  the  following  sieve  tests, 
the  sieves  being  used  in  the  order  named: 

3  per  cent,  of  the  whole  will  pass  No.  200  sieve. 
15  per  cent,  of  the  whole  will  pass  No.  100  sieve. 
1 8  per  cent,  of  the  whole  will  pass  No.  80  sieve. 
30  per  cent,  of  the  whole  will  pass  No.  50  sieve. 
24  per  cent,  of  the  whole  will  pass  No.  30  sieve. 
10  per  cent,  of  the  whole  will  pass  No.  10  sieve. 

and  none  will  fail  to  pass  the  No.  10  sieve.1 

49.  Pulverized  Stone. — This  may  consist  of  limestone  or  other 
sound  stone  or  sand,  pulverized  to  such  fineness  that  the  whole  will 
pass  the  No.  50  sieve,  not  more  than  ten  (10)  per  cent,  will  be  re- 
tained on  the  No.  100  sieve,  and  at  least  seventy  (70)  per  cent,  of  it 
will  pass   the  No.    200   sieve.     Portland  cement   may   be  partly 
substituted  for  pulverized  stone,  where  the  Engineer  shall  so  direct.2 
Portland  cement  thus  used  will  be  paid  for  at  the  price  bid  per  barrel 
for  the  same,  in  addition  to  the  price  paid  per  square  yard  for  the 
pavement  surface.     The  pulverized  material  must  be   thoroughly 
dry  when  used. 

50.  Asphaltic  Paving  Cement. — Asphalt  Paving  Cement  shall  be 
prepared  from  the  refined  asphalt  described  in  Sect.  44  and  the 
tempering  agent  described  in  Sect.  47.     The  refined  asphalt,  together 
with  the  asphalt  in  the  tempering  agent,  shall  constitute  not  less 
than  sixty  per  cent.  (60%)  of  the  asphaltic  cement. 

The  refined  asphalt  and  the  tempering  agent  shall  be  mixed  and 

1  It  is  now  well  recognized  that  the  character  and  quality  of  the  sand  used 
is  one  of  the  most  important  elements  in  determining  the  utility  and  durability 
of  an  asphalt  pavement.     A  satisfactory  sand  should  be  insisted  on,  even  if  it 
involves  a  very  considerable  increase  in  the  first  cost  of  the  work. 

While  our  knowledge  of  the  subject  is  not  complete,  experience  seems  to 
indicate  pretty  clearly  that  a  sand  of  the  quality  and  size-grading  here  specified 
as  typical,  may  be  depended  upon  to  produce  a  good  pavement. 

2  The  use  of  Portland  cement  in  surface  mixtures  to  be  laid  on  streets  of 
heavy  travel,  or  those  exposed  to  damp  foundations,  is  very  strongly  recom- 
mended.    On  streets  of  the  heaviest  travel,  or  where  the  pavement  will  be  ex- 
posed to  unfavorable  conditions  of  dampness,  particularly  if  the  pulverized  stone 
is  not  very  finely  ground,  the  Portland  cement  may  constitute  twenty  per  cent, 
of  the  pulverized  material,  or  "  dust,"  as  it  is  commonly  called.     Ordinarily  from 
five  to  ten  per  cent,  may  be  used  to  advantage  on  all  streets  of  moderately  heavy 
travel. 


40  STREET  ROADWA  Y  PA  VEMENTS 

melted  together  at  a  temperature  not  below  two  hundred  and  seventy  - 
five  degrees  F.  (275°  F.),  and  not  above  three  hundred  and  twenty- 
five  degrees  Fahrenheit  (325°  F.),  and  thoroughly  incorporated  by 
agitation  until  a  homogeneous  cement  is  produced.  The  agitation 
shall  be  continued  until  the  cement  is  used. 

The  asphaltic  cement  at  a  temperature  of  seventy-seven  degrees 
F.  (77°  F.)  shall  be  of  such  consistency  as  to  show  a  penetration  of 
from  forty  to  eighty  hundredths  of  a  centimeter,  as  the  engineer 
may  direct  for  each  street,  when  tested  with  the  standard  Dow 
penetration  apparatus,  using  a  number  two  cambric  needle  loaded 
with  one  hundred  grams.  When  a  cement  of  a  consistency  satis- 
factory to  the  engineer  has  been  produced  and  approved  for  any 
street  a  sample  of  it  shall  be  kept  as  a  standard  and  all  subsequent 
batches  or  kettles  must  be  made  to  conform  thereto,  suitable  ap- 
paratus and  tests  being  employed  to  determine  the  correspondence 
of  each  new  batch  with  the  standard.1  The  asphaltic  cement  when 
at  its  melting  temperature  shall  be  so  viscous  that  it  will  draw  out 
into  moderately  long  fine  threads  which  shall  be  free  from  lumps 
or  raggedness  and  shall  possess  satisfactory  adhesive  and  cementitious 
qualities.2 

51.  Composition  and  Preparation  of  Asphalt  Surface  Mixture. — 
The  surface  course  shall  be  composed  of  the  materials  specified  in 
Sections  43,  44,  45,  46,  47,  48,  49,  and  50  mixed  in  such  ratios  by 
weight  as  the  Engineer  may  direct  or  approve.  A  typical  mixture 
will  contain: 

1  For  determining  the  consistency  of  individual  batches  of  asphalt  paving 
cement  with  a  standard  sample,  the  flow-plate  method  is  most  convenient  and 
sufficiently  accurate.     For  a  description  of  the  latest  improved  form  of  this 
apparatus  see  Engineering  News  of  Aug.  22,  1912,  p.  347.     It  can  only  be  used, 
however,  where  the  cements  to  be  compared  are  of  the  same  general  compo- 
sition— the  same  refined  asphalt  and  tempering  agent — as  the  standard. 

2  The  practical  value  of  the  exact  determination  of  the  ductility  of  asphalt 
paving  cements  is  regarded  by  the  author  as  not  well  established.     It  is  cus- 
tomary, however,  in  most  recent  specifications  to  require  it.     Some  asphaltic 
cements  that  have  been  quite  successfully  used  for  pavements  have  not  compiled 
with  such  requirements,  while  good  coal-tar  pitches  will  greatly  exceed  them. 
Where  this  test  is  used  the  usual   specification  requires   that  a  briquette  of 
asphaltic  cement  having  a  cross-section  of  one  square  centimeter,  at  penetration 
50,  shall  elongate  to  the  extent  of  not  less  than  20  nor  more  than  85  centimeters 
at  77°  F.     If  the  asphaltic  cement  varies  from  50  penetration  an  increase  or  de- 
crease of  at  least  2  centimeters  will  be  required  for  each  five  points  above 
or  below  50  penetration  (Dow  apparatus  to  be  used). 


SHEET  ASPHALT  PAVEMENT  41 

Sand 100. o  Ibs. 

Pulverized  mineral  matter  passing  No.  200 
screen,  including  that  found  in  the  paving 
cement 1 7  •  5  Ibs. 

Pure  bitumen  (in  paving  cement) 13 . 5  Ibs. 

But  the  quantities  of  pulverized  stone  and  of  asphaltic  cement  shall 
be  varied  as  may  be  found  necessary  or  desirable  by  the  Engineer 
to  suit  the  purity  of  the  asphaltic  cement,  the  character  of  the  sand, 
the  climatic  conditions,  and  the  varying  quantity  and  character  of 
travel  on  the  street  to  be  paved;  and  Portland  cement  may  be  sub- 
stituted partly  or  wholly  for  the  pulverized  stone,  when  directed 
by  the  Engineer.  The  surface-course  mixture  shall  be  submitted 
to  the  Engineer  and  approved  by  him  before  any  is  laid  upon  the 
street. 

The  mixing  shall  be  accomplished  in  a  mechanical  mixing 
apparatus  capable  of  rapidly  and  effectually  incorporating  the  mate- 
rials together,  and  each  batch  must  remain  in  the  mixer  a  sufficient 
length  of  time  to  effect  a  perfect  mixture.  The  sand  shall  be 
separately  heated  and  shall  reach  the  mixing  apparatus  at  a  tem- 
perature not  above  three  hundred  and  fifty  (350)  degrees  F.,  nor 
below  three  hundred  and  twenty  (320)  degrees  F.  The  pulver- 
ized stone  shall  be  at  such  a  temperature  that  when  mixed  with 
the  sand  the  temperature  of  the  mixed  mass  shall  not  be  above 
three  hundred  and  fifty  (350)  degrees  F.,  nor  below  three  hun- 
dred and  twenty  (320)  degrees  F.  The  sand  shall  be  first  placed 
in  the  mixer,  followed  by  the  pulverized  stone,  and  these  two 
materials  shall  be  thoroughly  mixed  together  before  the  asphaltic 
cement  is  added.  The  asphaltic  cement  at  a  temperature  not  above 
three  hundred  and  fifty  (350)  degrees,  nor  below  three  hundred 
(300)  degrees  F.  shall  then  be  added  in  such  a  way  as  to  evenly 
distribute  it  over  the  sand  and  pulverized  stone,  and  the  mixing 
continued  until  the  materials  are  thoroughly  incorporated  into  a 
perfectly  uniform  and  homogeneous  mass,  with  the  grains  of  sand 
completely  covered  with  cement.  Suitable  thermometers  shall  be 
constantly  used  to  determine  the  temperatures  specified  herein. 
Great  care  must  be  taken  to  accurately  weigh  and  proportion  the 
materials  charged  into  the  mixer.1 

1  It  should  be  noted,  in  a  general  way,  that  there  is  quite  a  difference  in  the 
temperature  to  which  different  asphalts  may  be  safely  subjected. 

Trinidad  asphalt,  and  the  California  residual  pitches,  will  not  be  injured  by 


42  STREET  ROADWA  Y  PA  VEMENTS 

52.  Stone  for  Base-course. — Stone   screenings  for  base-course 
shall  be  of  crushed,  hard,  durable  stone.     The  portion  used  shall 
all  be  retained  upon  a  No.  8  sieve,  or  screen,  and  shall  all  pass  a 
screen  having  square  meshes,  the  linear  dimensions  of  the  openings 
in  which  are  one-half  (1/2)  inch  less  than   the   thickness   of  the 
base-course. 

53.  Composition    of    Base-course. — The    base-course    shall    be 
composed  of  the  crushed  stone  specified  in  Section  52,  mixed  with 
the  asphaltic  cement,  sand  and  pulverized  stone  specified  in  Sections 
50,  48  and  49,  but  the  asphaltic  cement  shall  be  of  such  hardness  as 
the  engineer  may  direct. 

A  typical  base-course  mixture  will  be  composed  as  follows: 

Crushed  stone 100         Ibs. 

Sand 42         Ibs. 

Pure  bitumen  (in  asphaltic  cement) 7         Ibs. 

Pulverized  stone 7  1/2  Ibs. 

But  the  mixture  shall  be  such  that  when  placed  on  the  street  and 
compressed  by  the  roller  the  mass  shall  be  dense  and  the  voids  in 
the  stone  completely  filled;  and  to  accomplish  this  the  quantity  of 
crushed  stone  used  in  the  mixture  may  be  increased  or  decreased, 
as  the  volume  of  its  voids  may  require,  in  order  that  they  may  be 
completely  filled.1 

54.  Mixing  the  Base-course. — The  materials  for  the  base-course 
shall  be  heated  and  mixed  in  the  same  general  manner  a*s  prescribed 
for  the  surface-course  (Sect.  51),  the  crushed  stone  being  delivered 
first  in  the  mixer.     The  temperature  of  the  mixture  as  it   comes 
from  the  mixer  being  not  above  three  hundred  and  twenty-five 
(325)  degrees  F.,  nor  below  three  hundred  (300)  degrees  F. 

55.  Laying    Asphalt    Pavement,    General. — Asphalt   pavement 
must  not  be  laid  except  when  the  surface  upon  which  it  is  to  be  placed 

the  higher  range  of  temperatures  named  in  these  specifications,  while  Bermudez 
and  some  other  asphalts  should  be  worked  at  as  nearly  as  possible  to  the  lower 
range  of  temperatures  named.  The  relative  amount  of  loss  of  the  different 
asphalts  when  exposed  for  seven  hours  to  the  temperature  of  325  degrees  (Sect. 
44)  will  supply  a  rough  practical  guide  as  to  the  temperature  permissible — the 
greater  the  loss,  the  closer  should  the  lower  range  of  temperatures  be  adhered  to. 
1  The  open  base-course,  or  "binder,"  composed  only  of  crushed  stone,  coated 
with  pitch  or  asphaltic  cement,  extensively  and  almost  exclusively  used  up  to 
a  recent  date,  is  no  longer  advocated  by  the  best  authorities  on  asphalt  pave- 
ments. The  aim  is  now  to  make  the  base-course  as  dense  and  strong  as  the 
surface-course. 


SHEET  ASPHALT  PAVEMENT  43 

is  dry;  nor  when  the  temperature  of  the  air  is  below  thirty- two  (32) 
degrees  F.,  or,  if  a  strong  wind  prevails,  when  the  temperature  of 
the  air  is  below  forty  (40)  degrees  F. 

The  pavement  mixture,  whether  for  base-  or  surface-course, 
shall  be  taken  to  the  street  as  soon  after  it  leaves  the  mixer  as  prac- 
ticable. When  the  temperature  of  the  air  is  below  seventy  (70) 
degrees  F.,  the  loaded  vehicles  conveying  the  mixture  to  the  street 
shall  be  covered  by  canvas  covers  to  prevent  the  escape  of  heat. 
When  unloaded  upon  the  street,  the  temperature  of  the  mass  should 
not  be  below  two  hundred  and  eighty  (280)  degrees  F.,  and  any 
load  or  portions  of  a  load  found  under  two  hundred  and  forty  (240) 
degrees  F.  must  be  rejected.  After  being  unloaded  on  the  street, 
the  mixture  must  be  shoveled  into  place  in  such  a  manner  that  the 
whole  of  it  will  be  moved  from  the  pile  into  which  it  was  unloaded. 

56.  Laying   the  Base-course. — The   base-course   will   have    an 
average  thickness  of  one  and  one-quarter  (i  1/4)  inches  after  compres- 
sion.    It  shall  be  laid  directly  upon  the  pavement  foundation,  which 
must  be  free  from  all  loose  fragments  and  rubbish  and  be  swept  clean 
in  advance  of  the  application  of  the  base-course.     The  base-course 
mixture  shall  be  spread  upon  the  foundation  and  evenly  and  regu- 
larly graded  to  such  a  depth  that  after  compression  by  the  roller 

its  surface  will  be inches  below,  and  truly  parallel 

to,  the  pavement  datum. 

Great  care  must  be  taken  in  handling,  spreading  and  grading 
the  mixture  to  maintain  the  uniform  admixture  of  the  crushed  stone 
throughout  the  mass.  The  rakes  used  must  have  tines  wide  apart, 
and  the  back  of  the  rake  must  be  principally  used  for  grading. 
Immediately  after  being  graded,  and  while  still  hot,  the  base-course 
shall  be  rolled  with  an  asphalt  roller  weighing  not  less  than  five 
tons,  the  rolling  being  continued  until  no  further  compression  takes 
place. 

The  base-course  must  not  be  laid  more  than  one  day's  work  in 
advance  of  the  surface-course. 

When  the  base-course  is  completed  it  must  present  a  uniform 
appearance  and  texture  over  the  whole  surface,  which  must  conform 
so  truly  to  the  designed  grade  and  contour  that  a  twelve-foot  tem- 
plate, when  applied,  will  show  no  departure  from  the  true  surface 
greater  than  one-quarter  (1/4)  inch. 

57.  Laying    the    Surface-course. — In     delivering    the    surface- 
course  mixture  upon  the  base-course,  care  must  be  taken  not  to 
break  or  disturb  the  latter.     Any  breaks  made  in  the  base- course 


44  STREET  ROADWA  Y  PA  VEMENTS 

must  be  so  repaired,  before  the  surf  ace -course  is  spread,  as  to  be 
equal  in  density  and  surface  to  the  adjoining  base. 

Before  the  surface-course  is  spread  the  base-course  must  be 
thoroughly  cleaned  and  all  rubbish,  loose  material  and  street  dirt 
removed. 

The  material  for  the  surface-course  shall  be  so  evenly  spread 
and  graded  with  asphalt  rakes  that  after  it  is  properly  compacted 
by  rolling,  the  surface  will  coincide  with  the  pavement  datum 
within  the  limits  named  below.  In  grading  the  material,  all  lumps 
must  be  broken  up  and  the  whole  reduced  to  a  finely  comminuted 
mass  of  equal  density  throughout.  Directly  after  being  so  graded 
it  shall  be  rolled  with  a  hand-roller,  or  light  steam-roller,  to  partly 
compress  the  material,  and,  when  so  directed  by  the  Engineer,  the 
surface  shall  then  be  ironed  with  smoothing  irons  heated  to  a  tem- 
perature that  will  melt,  but  not  burn,  the  asphaltic  cement.  A 
thin  layer  of  hydraulic  cement,  just  sufficient  to  prevent  adhesion 
between  the  material  and  the  roller,  shall  then  be  swept  over  the 
surface,  which  shall  at  once  be  thoroughly  rolled  with  a  ten-ton 
asphalt  roller  until  the  material  shall  be  thoroughly  compressed 
and  its  surface  be  brought  to  the  exact  grade  and  contour  designed 
for  the  street  surface.  The  work  of  the  ten-ton  steam-roller  must 
begin  before  the  material  has  cooled  below  two  hundred  (200) 
degrees  F.,  and  be  continued  until  the.  roller  makes  no  further 
impression  upon  the  surface.  The  first  course  of  the  heavy  rolling 
shall  be  parallel  to  the  street  beginning  at  the  curb  and  working 
toward  the  center  on  each  side,  after  which  it  should  be  diagonally 
rolled,  and  also  cross-rolled  if  the  width  of  the  street  permits.1  Any 
portions  of  the  surface  not  accessible  to  the  roller  shall  be  tamped 
with  hot  tampers  until  compacted  equally  with  the  rolled  portion. 
When  completed,  the  surface  shall  have  an  average  thickness  of 
inches  and  must  be  so  free  from  waves  or  irregu- 
larities that  a  template  not  less  than  twelve  feet  long,  when  applied 
to  the  street  surface  shall  nowhere  show  a  divergence  from  the 
designed  true  surface  of  more  than  three-sixteenths  (3/16)  inch, 
and  a  template  sixteen  (16)  feet  long  applied  to  the  gutters  shall 
show  no  divergence  from  the  true  gutter  grade  greater  than  one- 
eighth  (1/8)  inch. 

1  The  importance  of  proper  and  thorough  rolling  is  not  usually  fully  appre- 
ciated, and  this  part  of  the  work  is  often  shirked  by  the  contractor.  Not  only 
should  the  heavy  roller  be  at  work  as  soon  as  the  material  will  bear  it,  but  the 
roller  should,  when  work  is  progressing  regularly,  be  kept  at  work  all  the  time. 
It  is  a  safe  motto  that  the  final  rolling  cannot  be  overdone. 


SHEET  ASPHALT  PAVEMENT  45 

Before  the  surface-course  is  placed,  all  exposed  surfaces  of  curbs, 
crosswalks,  manholes,  etc.,  with  which  the  surface-course  will 
be  in  contact,  must  be  well  painted  with  hot  paving  cement  or 
approved  pitch.  The  street  shall  not  be  opened  to  travel  until  the 
pavement  has  become  cold  and  hard. 

58.  Street  Railroad  Tracks. — Where  railroad  tracks  exist  on  the 
streets,  the  sub-grade  and  the  pavement  foundation  shall   extend 
under  the  tracks,  uninterrupted  except  by  the  ties  and  other  struc- 
tures connected  with  the  track.     Where  concrete  foundation  is  used, 
special  care  must  be  taken  with  the  concrete  directly  under  or  around 
the  rails,  and  concrete  made  of  fine  crushed  stone  and  a  higher  ratio  of 
cement  and  sand  may  be  required  in  contact  with  the  rail.     The 
concrete  must  be  thoroughly  tamped  under  and  against  the  rail. 

The  asphalt  surface  shall  be  laid  directly  against  the  rails,  which, 
if  their  temperature  be  under  fifty  (50)  degrees  F.,  shall  be  heated 
by  suitable  appliances  to  a  temperature  of,  or  above,  sixty  (60) 
degrees  F.  immediately  before  the  asphalt  material  is  placed  around 
the  rail.  The  hot  asphalt  material  must  be  thoroughly  tamped 
against  and  along  the  rail  and  under  any  projecting  portions  of  it, 
and  the  surface  of  the  pavement  must  be  even  with,  or  slightly 
(not  more  than  one-eighth  (i/ 8)  inch)  above  the  top  of  the  rail. 
Slot-rails  will  be  treated  in  the  same  manner,  subject  to  such  modi- 
fications as  their  forms  may  necessitate.1 

59.  Plant. — The  plant  for  making  asphalt  paving  mixtures  must 
1  There  is  still  a  wide  difference  of  opinion  as  to  the  advisability  of  laying  the 

asphalt  surface  directly  against  the  rail,  many  engineers  preferring  to  set  one 
or  more  courses  of  paving  brick,  or  stone  paving  blocks  between  the  rail  and 
the  edge  of  the  asphalt.  The  writer's  experience  is  to  the  effect  that,  if  the 
work  is  properly  done,  the  first-named  form  of  construction  is  preferable.  If 
the  asphalt  be  laid  against  a  rail  so  cold  that  the  asphalt  material  in  contact 
with  or  near  the  rail  is  chilled  before  it  can  be  compressed,  the  work  will  neces- 
sarily be  unsatisfactory.  As  to  durability,  wheels  following  the  line  of  the  rail 
or  of  the  paving  blocks  will  sooner  or  later  form  a  rut  in  the  asphalt  which  will 
require  repair — and  there  is  not  much  difference  in  the  results.  The  attempts 
to  prevent  the  formation  of  ruts  by  setting  blocks  alternately  as  headers  and 
stretchers  is  not  always  successful,  even  when  the  work  is  well  done,  and  the 
difficulty  of  properly  compressing  the  tongues  of  asphalt  between  the  headers 
is  so  great  that  it  is  usually  not  well  done.  The  asphalt  settles  under  travel  or 
is  gouged  out,  leaving  a  streak  of  rough  pavement,  and  the  difficulty  and  cost 
of  repairs  is  considerably  increased.  When  paving  blocks  or  bricks  are  used, 
they  should  be  firmly  and  carefully  set  in  the  concrete  foundation.  Probably 
the  most  satisfactory  construction  of  this  kind  consists  of  two  or  three  lines 
of  the  best  paving  brick  set  with  their  length  parallel  to  the  rail.  It  is  somewhat 
easier  to  get  at  and  repair  rail  joints  with  this  construction. 


46  STREET  ROADWA  Y  PA  VEMENTS 

be  of  approved  modern  design,  adapted  to  do  the  work  properly,  and 
equipped  with  efficient  machinery.  It  shall  be  of  sufficient  capacity 
to  turn  out  at  least  twelve  hundred  square  yards  of  pavement  surface 
daily  without  crowding.  Weighing  and  measuring  devices  shall  be 
accurate  and  adapted  to  the  purpose,  and  must  be  frequently  tested 
and  adjusted.  Each  plant  must  be  supplied  with  the  apparatus 
necessary  to  make  all  determinations  and  tests  required  at  the  plant 
to  properly  conduct  the  work  in  accordance  with  these  specifications. 
Steam-rollers  must  be  properly  balanced  and  the  rolling  surface 
must  be  true  and  smooth.  All  the  street  tools  used  must  be  of 
approved  kind  and  quality  and  must  be  kept  in  good  working  order. 


ASPHALT  BLOCK  PAVEMENT 

60.  Sub-grade. — The  sub-grade  for  asphalt  block  pavement  shall 
be  prepared  as  specified  in  Sect.  26  of  these  specifications. 

61.  Foundation. — The  foundation  for  asphalt  block    pavement 
shall  be  hydraulic  concrete  or  broken  stone.1 

Concrete  foundation  shall  be  constructed  in  accordance  with 
Sections  28  to  37  inclusive  of  these  specifications  and  shall  have  a 
thickness  of inches. 

Broken  stone  foundation  shall  be  constructed  in  accordance  with 
Section  40  of  these  specifications  and  shall  have  a  thickness,  when 
completed  of inches. 

62.  Asphalt  Blocks. — Asphalt  blocks  shall  be  not  less  than  ten 
(10)  inches  nor  more  than  twelve  (12)  inches  long,  not  less  than 
four  (4)  nor  more  than  six  (6)  inches  wide  and  not  less  than  two  (2) 
inches  nor  more  than  four  (4)  inches  thick.     Blocks  for  the  same 
street  must  be  of  the  same  standard  size  throughout  and  individual 
blocks  shall  not  vary  in  any  dimension  more  than  three-sixteenths 
(3/16)  inch  from  the  standard  size.     Blocks  that  are  chipped,  cracked 
or  are  otherwise  defective  shall  be  rejected. 

63.  Material  and  Composition. — Asphalt  paving  blocks  shall  be 

1  The  practice  of  laying  asphalt  block  pavement  upon  crushed  stone,  or  a 
sand  foundation,  on  streets  carrying  a  considerable  travel,  is  inadvisable.  See 
foot-note,  page  23. 


ASPHALT  BLOCK  PAVEMENT  47 

composed  of  crushed  trap  rock1  or  equally  hard  and  durable  rock, 
sand,  pulverized  stone  and  asphaltic  cement. 

The  crushed  rock  shall  be  of  such  sizes  that  all  will  pass  a  screen 
having  circular  openings  one-third  (1/3)  inch  in  diameter  and  that 
all  will  fail  to  pass  a  number  ten  (No.  10)  sieve.  The  stone  shall  be 
freshly  crushed,  free  from  foreign  substances  and  clean  and  bright. 

The  sand  shall  be  clean  and  sharp  and  of  such  sizes  that  all  will 
pass  the  number  ten  sieve  and  not  more  than  five  per  cent,  will  pass 
the  number  two  hundred  sieve.  The  grain-size  of  the  sand  shall 
preferably  be  such  that  at  least  fifty  per  cent.  (50%)  of  it  will  pass 
the  number  eighty  sieve.  The  screenings  from  the  crushed  stone 
passing  the  number  ten  sieve  may  be  used  in  place  of  sand,  or 
thoroughly  mixed  with  the  sand  to  produce  a  mass  of  the  above 
composition.  The  pulverized  stone  shall  comply  with  Section  49 
of  these  specifications.  Portland  cement  shall  be  used  in  place  of 
not  more  than  ten  per  cent,  of  the  whole  if  directed  by  the  engineer, 
in  which  case  the  Portland  cement  will  be  paid  for  as  extra  work  at 
the  prevailing  market  price. 

The  asphaltic  cement  shall  comply  with  the  requirements  of 
Sections  43,  44,  45,  46,  47  and  50  of  these  specifications. 

64.  Typical  Composition. — A  typical  composition  of  the  blocks, 
which  must  be  complied  with  as  nearly  as  practicable,  is  as  follows; 
(by  weight) 

Bitumen 7  % 

Mineral  material  passing  No.  200  sieve 13% 

Mineral  material  passing  No.    80  sieve 9% 

Mineral  material  passing  No.    40  sieve 7  % 

Mineral  material  passing  No.    10  sieve 28% 

Mineral  material  passing  No.      3  sieve 36% 

100% 

65.  Manufacture. — The  crushed  rock,  sand  and  pulverized  stone 
shall  be  thoroughly  mixed  together  at  a  temperature  not  above 
three  hundred  and  seventy-five  degrees  Fahrenheit  (375°  F.)  and 
not   below   three   hundred   and    twenty-five    degrees   Fahrenheit 
(325°  F.)  and  the  asphaltic  cement,  at  a  like  temperature,  added 

1  Hard  limestone  may  be  used  where  trap  is  not  procurable  except  at  a  pro- 
hibitive cost;  but  unless  the  difference  in  cost  is  very  great  the  trap  will  be  the 
most  economical  in  the  end. 


48  STREET  ROADWA  Y  PA  VEMENTS 

and  the  mixing  continued  until  a  perfectly  uniform  mass  is  produced, 
with  every  fragment  of  stone  completely  coated  with  cement. 

The  hot  mixture  will  then  be  compressed  in  molds  under  a  pressure 
not  less  than  four  thousand  (4000)  pounds1  per  square  inch,  after 
which  t  the  blocks  will  be  removed  from  the  molds  and  allowed  to 
cool,  either  in  the  air  or  in  water. 

The  completed  blocks  after  cooling  in  air  shall  have  a  specific 
gravity  of  not  less  than  2.5.  They  shall  not  absorb,  when  immersed 
in  water  for  twenty-four  hours,  more  than  one-half  of  one  per  cent, 
of  water.  When  tested  in  the  standard  rattler  for  testing  paving 
brick  the  average  loss  by  abrasion  shall  not  exceed  twelve  per  cent. 
(12%)  of  their  original  weight,  after  1800  revolutions  of  the  rattler. 

66.  Laying  the  Blocks.2 — The  foundation  shall  be  first  cleaned  of 
dirt,  rubbish  or  loose  material. 

When  the  blocks  are  four  (4)  -inches  or  less  in  depth  as  laid,  they 
shall  be  set  upon  a  bed  of  mortar  made  and  applied  to  the  foundation 
in  the  following  manner: 

The  mortar  shall  be  composed  of  Portland  cement  and  sand, 
in  the  ratio  of  one  (i)  part  cement  to  three  (3)  parts  of  sand,  thor- 
oughly mixed  with  sufficient  water  to  make  a  rather  soft  mortar. 
This  mortar  shall  be  spread  over  the  foundation,  which  shall  be 
previously  wetted,  in  a  layer  approximately  one-half  (1/2)  inch 
thick  and  its  top  graded  by  the  use  of  templates  to  a  surface  at  such 
depth  below,  and  truly  parallel  to  the  pavement  datum,  that  when 
the  blocks  are  firmly  set  in  it  and  rammed  their  tops  will  be  in  the 
true  grade  and  contour  of  the  pavement.  The  mortar  shall  be  made 
and  spread  only  as  required  in  the  progress  of  block  laying,  and  any 
mortar  that  has  begun  to  set  before  the  blocks  are  in  place  and 
rammed,  shall  be  removed  and  fresh  mortar  substituted.  The  blocks 
shall  be  set  upon  this  mortar  bed  with  their  longest  dimension  across 
the  street,  in  continuous  courses  which  shall  be  straight  and  at  right 
angles  to  the  axis  of  the  street.  The  block  layers  must  stand  upon 
the  blocks  already  laid  and  not  upon  the  mortar.  The  blocks  and 
the  courses  of  blocks  shall  be  set  as  closely  together  as  practicable. 

1  The  pressure  commonly  specified  is  5000  Ibs  per.  square  inch,  but  recent 
investigations  make  it  doubtful  if  that  pressure  is  ever  attained,  or  is,  indeed, 
practicable  with  any  presses  so  far  constructed. 

2  Asphalt  blocks  are  now  very  commonly  laid  upon  their  sides,  even  where  they 
are  made  as  thin  as  two  inches,  on  streets  carrying  very  considerable  travel. 
The  practice  is  not  to  be  recommended  unless  the  blocks  are  at  least  four  inches 
thick.     Blocks  two  inches  thick  will  give  good  service  on  private  drive-ways 
and  streets  or  quite  light  travel. 


ASPHALT  BLOCK  PA  VEMENT  49 

Blocks  in  adjoining  courses  must  break  joint  not  less  than  four 
inches.  Whole  blocks  only  will  be  used,  except  as  fillers  at  the  ends 
of  the  courses  or  in  fitting  the  pavement  around  manholes  or  other 
structures,  and  where  thus  used  the  broken  ends  of  the  blocks  must 
be  dressed  to  make  close  joints.  Unless  otherwise  permitted,  each 
course  must  be  laid  continuously  across  the  street  without  inter- 
ruption in  time.  .As  each  course  is  completed  the  end  joints  shall 
be  forced  close  together  by  the  use  of  wedges,  levers  or  mauls. 
Upon  the  completion  of  every  third  course,  the  courses  shall  be  forced 
together  by  placing  a  timber  scantling  against  the  face  of  the  last 
course  and  striking  it  with  a  sledge  or  maul.  When  the  blocks  are 
thus  laid,  and  before  the  mortar  under  them  begins  to  set,  they  shall 
be  well  rammed  to  a  solid  bearing  in  the  mortar  with  a  wooden 
street  rammer  weighing  not  less  than  thirty  (30)  pounds,  a  two-inch 
plank  ten  (10)  inches  wide  and  three  (3)  feet  long  being  interposed 
between  the  block  and  the  rammer  and  moved  about  so  that  the  whole 
surface  shall  be  covered  and  rammed.  When  the  ramming  is  com- 
pleted, the  top  of  the  blocks  must  conform  so  closely  to  the  pavement 
datum  that  when  a  template  or  straight  edge  is  placed  upon  the 
pavement,  its  surface  shall  nowhere  depart  from  the  true  surface 
more  than  three-sixteenths  (3/16)  inch.  Blocks,  or  portions  of  the 
pavement  found  too  -high  or  too  low,  must  be  taken  up  and  reset  in 
fresh  mortar  to  the  true  grade.  When  thus  completed  to  the 
satisfaction  of  the  Engineer,  a  layer  of  one-half  (1/2)  inch  of  fine 
dry  sand  shall  be  placed  over  the  surface  and  swept  about  with 
brooms  until  all  joints  are  completely  filled.  The  remaining  sand 
shall  be  removed  from  the  pavement  at  such  time  as  the  Engineer 
may  direct. 

When  the  depth  of  the  blocks  exceeds  four  (4)  inches,  they  may 
be  set  upon  a  cushion-course  of  sand,  as  prescribed  for  brick  pave- 
ment, Section  86,  the  joints  to  be  filled  with  sand,  as  specified  above 
in  this  Section. 

67.  Railroad  Tracks. — Where  railroad  tracks  exist  on  the  street  to 
be  paved,  the  construction  shall  be  the  same  as  prescribed  for 
granite  block  pavement,  Section  78. 

68.  The  street  shall  not  be  opened  to  travel  until  the  mortar 
under  the  blocks  shall  have  become  fully  set,  and  in  no  case  under 
five  days  after  the  blocks  are  laid. 


50  STREET  ROADWA  Y  PA  VEMENTS 


GRANITE  BLOCK  PAVEMENT 

69.  Granite  block  pavement  shall  be  laid  upon  a  foundation  of 
hydraulic  cement  concrete.1 

70.  Sub -grade  and  Foundation. — The  sub-grade  shall  be  pre- 
pared as   specified   in  Section  26.     The  foundation  shall  be  con- 
structed in  accordance  with  the  requirements  of  Sections  28  to  38 
inclusive. 

71.  Granite  Blocks. — The  blocks   shall  be   made   from   sound, 
durable   granite,   of   uniform   texture,   composition   and   hardness 
throughout.     No  outcrop,  deteriorated,  soft,  brittle,  or  seamy  stone 
shall  be  used.     If  the  blocks  are  obtained  from  different  quarries, 
or  from  different  parts  of  the  same  quarry  where  the  quality  or 
appearance  of  the  rock  differs,  the  product  of  each  must  be  kept 
separate  and  laid  together  on  the  street.2 

The  blocks  shall  be  not  less  than  eight  (8)  nor  more  than  twelve 
(12)  inches  long,  not  less  than  three  and  one-half  (3  1/2)  nor  more 
than  four  and  one-half  (4  i/  2)  inches  wide,  and  not  less  than  four 
and  three-quarters  (4  3/4)  nor  more  than  five  and  one-quarter 
(5  i/ 4)  inches  deep.3  They  shall  be  well-shaped,  rectangular,  with 
full  edges  and  corners.  Their  tops  shall  not  depart  more  than  one- 
fourth  (1/4)  inch  from  a  true  plane,  and  their  sides  shall  be  dressed 
so  that  joints  between  the  courses  will  nowhere  exceed  three-fourths 
(3/4)  inch  wide,  and  their  ends  so  that  end  joints  shall  not  exceed 

1  Granite  block  pavement  is,  as  a  rule,  used  upon,  and  appropriate  for  streets 
of  the  heaviest  class  of  travel,  and  should,  therefore,  be  provided  with  the  best 
and  strongest  foundation.     It  is  nearly  always  poor  economy  to  lay  granite 
blocks  upon  a  broken  stone,  gravel,  or  sand  foundation.  . 

2  Like  other  stones,  granite  from  various  localities  differs  widely  in  strength, 
hardness   and   brittleness.     Great   hardness,    accompanied   with    comparative 
brittleness,   is   not   desirable    in   granite   for  paving   blocks.     Such   material 
usually  polishes  by  travel  and  becomes  quite  slippery,  and  it  is  likely  to  become 
"turtle-backed,"  that  is,  the  corners  are  likely  to  be  chipped  off  or  worn  off, 
making  the  pavement  very  rough  and  uneven.     The  quality  of  the  granite 
to  be  used  in  any  one  city  is  generally  determined  by  the  available  supply,  and 
specifications  must  be  drawn  with  reference  thereto. 

3  Except  on  streets  of  excessively  heavy  travel  there  seems  to  be  no  good 
reason  for  making  the  blocks  more  than  five  inches  deep.     Blocks  of  this  depth 
are  quite  sure  to  become  deformed  by  irregular  wear  before  the  pavement  will 
need  to  be  renewed. 


GRANITE  BLOCK  PAVEMENT  51 

one-half  (1/2)  inch  wide.1  The  size  of  the  blocks  may  be  varied 
where  necessary  to  fit  the  pavement  against  or  around  bridge  stones 
or  other  street  structures. 

72.  Sand  Cushion. — The  foundation  shall  be  cleaned  of  all  dirt 
and  rubbish.     There  shall  then  be  spread  evenly  over  it  a  layer  of 
clean,  coarse  sand  to  a  uniform  depth  of  one  and  one-half  (i  1/2) 
inches. 

73.  Setting  the  Blocks. — The  blocks  shall  be  set  in  this  bed  of 
sand  perpendicular  to  the  street  surface,  with  their  length  at  right 
angles  to  the  street,  in  courses  extending  entirely  across  the  street, 
and  at  right  angles  to  its  axis,  except  at  street  intersections  where 
the  courses  shall  be  arranged  as  the  Engineer  may  direct.2     Only 
stones  of  the  same  width  shall  be  set  in  the  same  course.     The  stones 
in  each  course,  and  in  adjoining  courses,  shall  be  set  firmly  against 
each  other.     The  blocks  shall  be  set  in  the  sand  bed  in  such  a  man- 

1  The  widths  of  joints  here  specified  as  allowable  are  based  upon  the  assumption 
that  they  will  be  filled  with  Portland  cement  grout  as  specified  in  Sect.  75. 
If  this  grout  filling  is  used  narrower  joints  are  not  necessary,  as  the  grout  has 
sufficient  strength  to  support  the  corners  of  the  blocks,  and  sufficient  hardness 
to  resist  the  wear  of  travel  (largely  protected  as  it  is  by  the  blocks  themselves) 
and  to  cause  the  blocks  to  wear  down  quite  evenly. 

In  many  European  cities  the  specifications  require  much  closer  joints.  The 
granite  there  available  appears  to  break  out  naturally  to  truer  lines  and  better 
surfaces  than  that  used  in  the  Eastern  states,  at  least,  so  that  the  cost  of  dressing 
the  blocks  abroad  is  not  as  great  as  here. 

The  City  of  New  York  has  recently  adopted  specifications  for  "Special 
Improved"  Granite  Block  pavement  intended  to  approximate  the  Liverpool 
standard.  These  require  that  the  blocks  shall  be  not  less  than  6  nor  more  than 
ten  inches  long,  not  less  than  3  1/2  nor  more  than  4  1/2  inches  wide  and  five 
inches  in  depth.  "The  blocks  are  to  be  rectangular  with  tops  and  sides  uniform 
in  thickness,  to  lay  closely,  and  with  fair  and  true  surface,  free  from  bunches 
and  so  cut  or  dressed  that  when  laid  stone  to  stone  the  joints  shall  not  exceed 
3/8  of  one  inch.  The  head  of  the  block  shall  be  so  cut  that  it  shall  not  have 
more  than  one-quarter  of  an  inch  depression  from  a  straight  edge  laid  in  any 
direction  across  the  head  and  held  parallel  to  the  general  surface  of  the  block." 
The  joints  are  filled  with  bituminous  cement. 

The  above  specification  is  very  difficult  to  meet  from  the  granite  available 
to  New  York  without  excessive  and  expensive  cutting,  and  examination  of  the 
pavements  laid  under  these  specifications  shows  that  the  joints  greatly  exceed 
the  width  specified. 

It  is  believed  that  equally  good  results  may  be  secured  by  permitting  somewhat 
wider  joints  filled  with  grout,  and  the  cost  would  be  materially  reduced. 

2  The  most  satisfactory  arrangement  of  courses  at  street  intersections  is  that 
shown  by  Fig.  14,  page  208,  Til] son's  Street  Pavements  and  Paving  Materials, 
2d  edition. 


52  STREET  ROA  DWA  Y  PA  VEMENTS 

ner  that  their  bottom  surface  shall  rest  evenly  upon  the  sand  and 
that  their  tops  shall  be  even  with  each  other  and  to  such'an  elevation 
that  after  the  pavement  is  rammed,  as  hereinafter  directed,  its  gen- 
eral surface  shall  conform  closely  to  the  pavement  datum.  Stones 
in  adjoining  courses  shall  break  joint  not  less  than  three  (3)  inches. 

74.  Ramming.1 — After  the  blocks  are  set  each  individual  block 
shall  be  thoroughly  rammed  to  give  it  a  firm  bearing  in  the  sand 
and  to  bring  its  top  to  the  prescribed  pavement  datum.     The  ram- 
mers used  shall  have  wooden  faces  not  more  than  four  inches  in 
diameter,  and  shall  weigh  not  less  than  thirty  (30)  pounds.     Blocks 
or  sections  of  blocks  whose  tops  under  the  ramming  remain  above 
or  sink  below  the  pavement  datum  shall  be  taken  up  and  reset  so 
that  after  the  ramming  is  completed  their  tops  shall  coincide  with 
the  pavement  datum. 

75.  Filling  the  Joints.2 — After  the  ramming  specified  in  Sect.  74 
shall  have  been  completed,  the  joints  between  the  paving  blocks 
shall  be  filled  in  the  following  manner: 

All  the  joints  for  a  distance  of  three  feet  out  from  the  curbstones, 
and  three  contiguous  joints  continuous  across  the  street,  with  the 
included  end  joints,  at  intervals  of  about  fifty  (50)  feet  in  the 
length  of  the  street,  shall  be  filled  with  gravel  and  bituminous 
paving  cement.  The  gravel  used  shall  be  of  such  size  that  all  will 
pass  through  a  screen  having  five-eighths  (5/8)  inch  meshes,  and 
all  will  be  held  on  a  screen  having  one-fourth  (1/4)  inch  meshes. 
When  used,  the  gravel  must  be*  free  from  refuse  and  street  dirt. 

1  The  practice  of  filling  the  joints  with  gravel  to  a  depth  of  one  inch  or  more 
before  the  blocks  are  rammed  is  of  doubtful  utility.     If  the  blocks  are  set  closely 
against  each  other  they  will  be  well  held  in  place  while  the  ramming  proceeds. 
In  practice  it  is  hardly  possible  to  closely  gage  the  depth  of  such  preliminary 
gravel  filling,  and  the  top  or  final  filling  whether  of  grout  or  of  gravel  and  bitumi- 
nous cement,  is  likely  to  vary  greatly  in  depth,  and  the  lateral  support  of  the 
blocks  is  thus  likely  to  vary  in  strength  and  rigidity. 

2  It  has  been  the  almost  universal  custom,  in  this  country  at  least,  to  fill  the 
joints  in  granite  paving  either  with  gravel  alone  or  with  gravel  and  bitumi- 
nous cement.     But  the  reasons  that  have  led  engineers  to  prefer  grout  filling 
for  brick  pavements  apply  with  equal  force  to  granite  pavement.     It  makes  a 
stronger  and  harder  filling  than  the  gravel  and  bituminous  cement,  and  gives  a 
better  support  to  the  edges  of  the  paving  blocks,  thus  tending  to  prevent  chipping 
and  "turtle-backing"  in  the  pavement.     It  is  also  a  materially  cheaper  filling 
than  the  gravel  and  bituminous  cement.     But  to  provide  for  the  expansion  and 
contraction  of  the  pavement  by  changes  of  temperature,  it  is  desirable  that  a 
strip  in  the  gutters,  and  an  occasional  strip  across  the  whole  street,  shall  be  filled 
with  the  more  yielding  material,  as  specified. 


GRANITE  BLOCK  PAVEMENT  53 

The  bituminous  paving  cement  shall  be  composed  by  weight  of 
straight-run  coal  tar  pitch  of  the  hardness  commonly  known  as 
number  six,  to  which  has  been  added  and  thoroughly  mixed,  while 
both  are  in  a  melted  condition,  twenty  per  cent.  (20%)  by  weight 
of  refined  Trinidad  asphalt,  or  other  asphalt,  equal  for  the  purpose, 
and  twenty  per  cent.  (20%)  by  weight  of  Portland  cement.  These 
ingredients  must  be  thoroughly  mixed,  and  kept  agitated  until 
used.1 

The  joints  will  first  be  filled  with  the  gravel,  which  shall  be  per- 
fectly dry,  and  heated  so  that  when  put  in  the  joints  it  will  be  at  a 
temperature  of  about  three  hundred  (300)  degrees  F.  The  paving 
cement,  heated  to  a  temperature  of  about  three  hundred  (300) 
degrees  F.,  shall  be  at  once,  while  the  gravel  is  still  hot,  poured 
from  a  spouted  vessel  into  the  joints  until  the  interstices  of  the  gravel 
are  entirely  filled  to  the  surface  of  the  pavement,  repouring  being 
resorted  to  to  accomplish  this  result  whenever  necessary. 

All  the  joints  in  the  pavement  other  than  those  named  above 
shall  then  be  completely  filled  with  Portland  cement  grout,  in  the 
following  manner: 

The  grout  shall  be  composed  of  equal  parts  by  volume  of  sand 
(Sect.  30)  and  Portland  cement  (Sect.  29),  a  quick-setting  cement 
being  preferred.  The  sand  and  cement  shall  be  first  thoroughly 
mixed  dry  and  then  enough  water  added  to  make  a  grout  of  such 
consistency  that  it  will  flow  like  thick  cream,  and  the  mixing  con- 
tinued until  a  homogeneous  mass  is  produced  and  until  the  grout 
is  applied  to  the  pavement.  The  grout  shall  be  prepared  in  water- 
tight boxes  of  a  convenient  size.  Before  applying  the  grout  the 
pavement  shall  be  thoroughly  dampened  by  sprinkling.  The  grout 
shall  be  removed  from  the  mixing  box  and  spread  over  the  pave- 
ment with  scoop  shovels,  in  two  courses,  the  first  being  sufficient 
to  about  half  fill  the  joints,  and  the  second,  which  shall  be  applied 
before  the  first  has  begun  to  set,  shall  be  sufficient  to  entirely  fill 
the  remaining  space  in  the  joints.  As  the  grout  is  applied  to  the 
pavement  it  shall  be  swept  about  with  brooms  until  it  all  enters 
the  joints. 

1  The  object  of  adding  asphalt  and  Portland  cement  is  to  make  the  cement 
stronger  and  less  susceptible  to  changes  of  temperature.  Pure  coal-tar  pitch 
is  very  brittle  at  low  temperatures,  and  is  liable  to  flow  from  the  crown  of  the 
street  to  the  gutters  in  hot  summer  weather.  A  cement  made  as  here  specified 
is  not  only  much  stronger  and  less  brittle  in  cold  weather,  but  requires  a  mate- 
rially higher  temperature  to  cause  it  to  flow  than  does  pure  pitch. 
5 


54  STREET  ROADWA  Y  PA  VEMENTS 

76.  Order  of  Work. — The  sand  bed  shall  not  be  put  in  place  more 
than  fifty  (50)  feet  ahead  of  the  block  setters.     The  ramming  and 
filling  of  the  joints  shall  follow  closely  the  block  setting,  but  no  ram- 
ming shall  be  done  within  less  than  six  (6)  feet  of  the  face  of  the 
block  setting;  and  the  final  joint  filling  shall  be  kept  completed  to 
within  twenty-five  (25)  feet  of  the  ramming;  except  that  all  the 
work  rammed  during  any  day  shall  have  the  joint  filling  completed 
before  the  cessation  of  work  on  that  day.     The  street  shall  not  be 
opened  to  travel  until  the  grout  has  thoroughly  set. 

77.  Fitting  Paving  Around  Other  Structures. — The  size  of  blocks 
and  the  width  of  courses  shall,  as  the  block  laying  approaches  bridge 
stones,  curbs  and  other  structures,  or  in  making  closures  with  other 
sections  of  pavement,  be  so  selected  and  adjusted  that  joints  not 
over  three-quarters  (3/4)  inch  in  width  shall  result,  without  breaking 
blocks  or  splitting  courses. 

78.  Street  Railroad  Tracks. — Where  railroad  tracks  exist  in  the 
street  the  paving  blocks  shall  be  laid  against  the  rail  in  the  following 
manner: 

The  sub-grade  and  the  pavement  foundation  shall  extend  under 
the  rails  uninterrupted  except  by  the  ties  or  other  structures  con- 
nected with  the  railroad  track.  For  a  distance  of  sixteen  (16) 
inches,  on  each  side  of  the  rail,  measuring  from  the  center  thereof, 
there  shall  be  spread  on  the  pavement  foundation  a  layer  of  mortar 
not  less  than  one  and  one-half  (i  1/2)  inches  thick,  composed  of  one 
(i)  part  of  cement  and  three  (3)  parts  sand,  complying  with  the 
requirements  of  Sections  29  and  30.  Upon  this  layer  of  mortar  shall 
be  set,  against  the  rail,  and  on  each  side  of  it,  selected  paving 
blocks,  securely  bedded  in  the  mortar  before  it  shall  have  begun  to 
set.1  Alternate  blocks  shall  be  long  and  short  so  as  to  break  joint 
with  the  blocks  of  the  adjoining  pavement.  Selected  blocks  with 
well  dressed  top  surfaces  shall  be  used  and  their  tops  shall  be  set 
as  nearly  as  practicable  at  the  level  of  the  top  of  the  rail,  but  not  so 
high  that  the  car  wheels  will  ride  upon  them.  In  setting  the  blocks 
they  shall  be  firmly  bedded  into  the  mortar  by  the  use  of  paving 
hammers,  but  they  shall  not  be  thereafter  rammed.  As  the  blocks 
are  set,  any  space  between  the  paving  blocks  and  the  web  of  the  rail 
shall  be  filled  with  mortar  of  the  quality  described  above.  The 

1  As  the  wheels  of  vehicles  frequently  follow  along  the  lines  of  the  rails,  thus 
concentrating  their  effect  on  a  narrow  strip  near  the  rails,  and  as  the  continuous 
joint  against  the  rail  makes  the  pavement  weaker  there,  the  mortar  bed,  and 
the  greater  care  in  setting  the  blocks  along  and  near  the  rail  are  advisable. 


GRANITE  BLOCK  PAVEMENT  55 

placing  of  these  blocks  shall  not  precede  by  more  than  ten  (10) 
feet  the  block  laying  on  the  street.  Care  must  be  taken  not  to 
disturb  the  bedding  of  these  blocks  in  the  laying  of  the  adjoining 
pavement,  or  otherwise.  The  joints  shall  be  rilled  with  grout  as 
specified  in  Sect.  75. 

The  construction  along  slot-rails  shall  be  the  same  as  described 
above,  except  that  blocks  of  special  size  or  shape  may  be  required, 
as  the  Engineer  may  direct. 

79.  Bridge  Stone  Crossings. — Where  directed  by  the  Engineer, 
the  old  bridge  stone  shall  be  redressed  and  relaid,  as  hereinafter 
specified  for  new  bridge  stone,  and  shall  be  moved  from  the  point 
where  taken  up  to  the  point  where  they  are  to.be  relaid,  by  the 
Contractor  at  his  expense. 

New  bridge  stone  shall  be  of  the  same  quality  of  granite  as  the 
paving  blocks  and  free  from  imperfections.  They  shall  not  be  less 
than  three  and  one-half  (3  1/2)  nor  more  than  six  (6)  feet  long, 
eighteen  (18)  inches  wide  and  of  a  uniform  thickness  not  less  than 
six  (6)  nor  more  than  eight  (8)  inches,  but  these  dimensions  may 
be  varied  by  the  Engineer  where  necessary  to  fit  the  stone  into 
special  locations. 

Their  top  shall  be  well  dressed  to  a  true  plane  surface  not  varying 
in  evenness  more  than  one-quarter  (1/4)  inch.  The  sides  shall  be 
dressed  perpendicular  to  the  face  so  as  to  joint  closely  against  the 
paving  blocks.  The  ends  shall  be  cut  to  lines  making  an  angle  of 
from  60°  to  45°  with  the  longitudinal  axis  of  the  stones1  and  so 
dressed  and  to  such  a  bevel  that  when  set  in  the  curved  surface 
of  the  street,  the  joint  between  adjoining  stones  shall  not  be  wider 
than  three-eighths  (3/8)  inch  from  top  to  bottom. 

Bridge  stones  shall  be  set  in  advance  of  the  block  laying,  over  the 
concrete  street  foundation,  in  a  bed  of  sand  or  gravel  in  which  they 
thall  be  firmly  bedded.  Their  upper  surface  shall  conform  truly 
so  the  pavement  datum.  They  shall  be  set  accurately  to  the  lines 
given  by  the  Engineer.  Where  the  crosswalk  requires  more  than 
one  width  of  bridge  stone,  the  courses  shall  be  laid  parallel  to,  and 
at  such  distance  from  each  other  as  the  Engineer  may  direct,  and 
the  space  between  courses  shall  be  filled  with  paving  blocks  laid  as 
specified  for  other  parts  of  the  street. 

1  If  the  joints  are  parallel  to  the  direction  of  travel  on  the  street  the  wheels  of 
vehicles  are  more  likely  to  abrade  or  break  off  the  corners  of  the  stone  and  form 
incipient  ruts. 


56  STREET  ROADWA  Y  PA  VEMENTS 


BRICK  PAVEMENT 

80.  Sub-grade. — The  sub-grade  for  brick  pavement  shall  be  pre- 
pared in  accordance  with  Sect.  26,  and  shall  be  finished  to  a  surface 
inches  below  and  parallel  to  the  pavement  datum. 

81.  Foundation. — The  foundation  for  brick  pavement  shall  be  of 
•  hydraulic  concrete2  prepared  in  accordance  with  Sections  28  to  37 

inclusive.     Its  thickness  shall  be inches  and  its  upper 

surface  shall,  when  completed,  be  parallel  to  and  at  a  depth  below 
the  pavement  datum  equal  to  the  depth  of  the  brick  plus  one  and 
one-fourth  (i  1/4)  inches.  The  surface  of  the  foundation  shall  not 
vary  more  than  one-half  (1/2)  inch  above  or  below  that  depth. 

82.  Paving  Brick. — The  linear  dimensions  of  paving  brick  may 
vary  between  the  following  limits:  In  length,  from  eight  and  one- 
half  (8  1/2)  to  nine  and  one-half  (9  1/2)  inches;  in  width,  from  two 
and  one-fourth  (2  1/4)  to  three  and  one-half  (3  1/2)  inches;  in  depth, 
from  four  (4)  to  four  and  one-eighth  (4  1/8)  inches;  but  the  length 
shall  not  be  less  than  two  and  one-half  (2  1/2)  nor  more  than  three 
and  three-fourths  (3  3/4)  times  the  width.3     The  corners  shall  all 
be  rounded  off  to  a  radius  of  not  less  than  one-eighth  (1/8)  nor  more 
than  three-sixteenths  (3/16)  inch.     The  brick  for  any  one  contract 
shall  be  all  of  the  same  kind  and  of  the  same  standard  size,  and  the  in- 
dividual bricks  shall  not  vary  in  length  more  than  three-sixteenths 
(3/16)  inch,  nor  in  width  more  than  one-eighth  (1/8)  inch  from  the 
size  adopted  as  standard.     Raised  lugs  or  letters  are  permissible  on 
one  side  of  each  brick  but  must  not  project  more  than  three-sixteenths 
(3/16)  inch  from  the  general  surface.4 

1  These  specifications  conform  in  most  particulars  to  those  adopted  by  the 
"Association  for  Standardizing  Paving  Specifications,"  and  are  substantially 
the  same  as  those  recommended  by  the  "National  Paving  Brick  Manufacturers' 
Association"  though  they  differ  in  some  details  from  each.     The  latest  specifica- 
tions adopted  by  the  Association  for  Standardizing  Paving  Specifications  are 
very  full  and  satisfactory  and  are  to  be  highly  commended. 

2  Here  again  a  good  concrete  foundation  is  recommended,  as  being  in  the  end 
the  most  satisfactory  and  economical.     See  foot-note,  page  23. 

3  The   Association   for   Standardizing   Paving   Specifications    (New   Orleans 
meeting)  adopted  a  standard  size  for  paving  bricks  and  blocks  as  follows :     Paving 
brick,  8  1/2  inches  long,   21/2  inches  wide  and  4  inches  in  depth.     Paving 
blocks  8  1/2  inches  long,  3  1/2  inches  wide  and  4  inches  deep.     There  seems  to 
be  no  sufficient  reason  for  confining  the  brick  to  these  dimensions. 

*  The  specifications  of  the  Association  for  Standardizing  Paving  Specifications 
require  that  all  paving  brick  shall  have  lugs  on  one  side,  and  allow  a  projection 


BRICK  PA  VEMENT  57 

The  brick  must  be  specially  manufactured  for  paving  purposes. 
They  may  be  made  from  shale  or  from  suitable  clay.  In  either  case 
the  material  must  be  thoroughly  pulverized,  mixed  and  tempered, 
and  must  be  free  from  lime  nodules  or  other  substances  that  may 
disintegrate  the  brick  when  immersed  in  water.  The  brick  shall  be 
molded  in  efficient  brick  machines  to  a  truly  rectangular  form,  free 
from  cracks,  flaws  and  injurious  laminations.  After  being  dried 
the  brick  shall  be  properly  and  uniformly  burned  in  down- draft 
kilns.  Shale  brick  shall  be  burned  to  the  point  of  incipient 
fusion  or  vitrification.  After  the  burning  is  completed,  the  brick 
shall  be  allowed  to  cool  with  sufficient  slowness  to  insure  thorough 
annealing. 

The  completed  brick  shall  be  free  from  flaws,  cracks,  ragged 
corners,  and  from  such  distortion  or  warping  as  will  interfere  with 
their  utility  or  good  appearance  in  the  pavement.  Paving  brick 
shall  not  be  salt-glazed. 

83.  The  brick  shall  be  subjected  to  the  following  tests  to  determine 
their  quality: 

When  broken  by  the  blows  of  a  hammer  the  brick  shall  be  strong 
and  tough.  The  broken  surface  shall  show  a  homogeneous  compo- 
sition throughout  the  broken  section,  free  from  flaws,  injurious 
laminations,  nodules  and  voids,  and  shall  appear  to  be  uniformly 
burned  from  surface  to  center. 

When  subjected  to  the  standard  "Rattler"  test,  in  accordance 
with  the  rules  adopted  by  the  National  Paving  Brick  Manufacturers' 
Association,  the  average  loss  in  weight  shall  not  exceed  eighteen  (18) 
per  cent  1  and  the  loss  in  weight  of  any  individual  brick  in  the  test 
shall  not  be  more  than  twenty-five  (25)  per  cent,  greater  than  the 
average  loss  of  the  whole  charge. 

When  subjected  to  the  absorption  test,  in  accordance  with  the 
rules  adopted  by  the  National  Paving  Brick  Manufacturers'  Asso- 
ciation, shale  bricks  shall  not  absorb  more  than  two  (2)  per  cent,  nor 

of  1/4  inch  from  the  face  of  the  brick.  The  object  is  to  provide  a  wider  joint  be- 
tween the  bricks  in  order  to  facilitate  the  filling  of  the  joints.  The  author  does 
not  believe  these  lugs  necessary,  nor  that  brick  without  lugs,  but  otherwise 
acceptable,  should  be  excluded.  It  is  certain  that  many  of  the  best  brick  pave- 
ments ever  constructed  have  been  built  of  bricks  without  lugs.  If  lugs  are 
required  they  should  preferably  not  project  more  than  one-eighth  inch.  The 
same  reasons  that  make  narrow  joints  desirable  in  other  block  pavements  apply 
equally  to  brick  pavements. 

1  The  A.  S.  P.  S.  Specifications  permit  a  loss  of.  22%  with  the  block  size,  but 
do  not  name  a  permissible  loss  for  "brick"  size. 


58  STREET  ROA  DWA  Y  PA  VEMENTS 

less  than  one-half  (1/2)  of  one  per  cent,  of  their  weight  of  water,1  and 
clay  bricks  shall  not  absorb  more  than  six  (6)  per  cent,  of  their 
weight  of  water;  the  absorption  of  any  individual  brick  shall  not 
be  more  than  fifty  (50)  per  cent,  greater  than  the  mean  absorption 
of  the  whole  lot  tested.2  Brick  that  do  not  successfully  pass  all  these 
tests  will  not  be  accepted. 

84.  Samples. — Where  samples  of  paving  brick  have  been  required 
and  submitted  by  successful  bidders,  and  tested  as  described  above, 
it  will  be  assumed  that  these  samples  fairly  represent  the  quality  of 
the  brick  to  be  subsequently  supplied  for  the  work,  and  brick  that 
do  not  come  up  to  the  standard  thus  established  will  not  be  accepted. 

85.  Delivering  Brick  on  Street. — Unless  the  sidewalks  are  too 
narrow  to  permit  of  it,  the  brick  shall  all  be  delivered  upon  the 
street  before  the  foundation  is  constructed,  and  neatly  piled  upon 
the  outer  edge  of  the  sidewalks;  occasional  openings  being  left  in 
the  piles  for  the  accommodation  of  foot  passengers.     One-half  the 
brick  required  shall  be  thus  delivered  and  piled  upon  each  sidewalk. 
In  delivering  the  bricks  from  these  piles  to  the  bricklayers,  they  must 
be  carried  on  pallets,  or  other  suitable  devices  must  be  used  to  pre- 
vent mutilation  by  rough  handling;  they  must  not  be  dumped  from 
wheelbarrows  upon  freshly-laid  brick  pavement. 

If  for  any  reason  the  bricks  are  not  delivered  before  the  foun- 
dation is  laid,  or  if  the  sidewalks  are  too  narrow  to  permit  of  the 
brick  being  stored  upon  them,  they  may^be  delivered  over  the  foun- 
dation, but  not  until  the  concrete  has  set  so  hard  that  it  will  not  be 
injured  by  transportation  over  it. 

86.  Sand  Cushion. — Directly  before  the  brick  are  laid  into  the 
pavement  there  shall  be  spread  over  the  foundation  a  layer  of  sand 
one  and  one-half  (i  1/2)  inches  in  depth.     The  sand  shall  be  free 
from  vegetable  or  other  refuse  matter,  and  shall  not  contain  more 
than  five  (5)  per  cent,  of  clay  and  loam.     Pebbles  and  fragments 
of  stone  exceeding  one-fourth  inch  in  diameter  must  be  screened  out. 
When  spread  on  the  street  the  sand  shall  be  sufficiently  dry  to  per- 
mit of  proper  gaging  by  templates,  as  hereinafter  described.     The 
sand  shall  be  spread  and  correctly  gaged  to  the  proper  thickness 
and  surface  by  the  use  of  templates  formed  to  the  true  designed 

1  Absorption  of  less  than  one-half  of  one  per  cent.,  usually  indicates  that  a  shale 
brick  has  been  over-burned,  resulting  in  increased  brittleness. 

2  The  absorption  test  is  falling  into  disfavor,  particularly  with  the  manufac- 
turers.    The  author  believes  that  it  possesses  a  distinct  value  and  should  be 
retained. 


BRICK  PAVEMENT  59 

cross-sectional  contour  of  the  pavement.  If  the  width  of  the  street 
between  curbs  does  not  exceed  twenty-five  (25)  feet,  the  template 
shall  be  made  in  one  length  sufficient  to  cover  the  full  width  of  the 
street,  and  its  ends  shall  be  so  constructed  and  fitted  with  iron  rollers, 
that  it  will  rest  upon  and  roll  along  the  top  of  the  curb  at  each  end; 
if  the  width  of  the  street  between  curbs  be  not  more  than  fifty  (50) 
feet,  the  template  shall  be  of  sufficient  length  to  reach  from  the 
curb  to  the  middle  of  the  street,  and  constructed  to  move  on  rollers 
on  top  of  the  curb  at  one  end  and  upon  a  plank  six  (6)  inches  wide 
and  one  and  one-half  (i  1/2)  inches  thick  laid  upon  the  foundation 
along  the  center  line  of  the  pavement.  The  template  shall  be  worked 
forward  and  backward  along  the  line  of  the  street  until  the  surface 
of  the  sand  conforms  exactly  to  the  designed  contour  of  the  pave- 
ment, at  a  depth  below  the  pavement  datum  equal  to  the  depth  of 
the  paving  brick  minus  one-fourth  (1/4)  inch.  The  whole  surface 
shall  then  be  rolled  with  a  garden  roller  not  less  than  thirty-six 
inches  long  and  not  less  than  thirty  inches  in  diameter,  weighing 
not  less  than  three  hundred  pounds.  When  completed  the  surface 
of  the  sand  cushion  shall  be  smooth  and  unbroken,  and  care  must  be 
taken  not  to  disturb  it  before  the  bricks  are  set  upon^it. 

87.  Setting  the  Brick. — Several  courses  of  brick,  aggregating  a 
strip  having  a  width  of  not  less  than  twelve  (12)  inches  nor  more 
than  fifteen  (15)  inches  on  each  side  of  the  street,  beginning  against 
the  curb,  shall  be  first  laid;  the  brick  being  set  with  their  long  dimen- 
sion parallel  to  the  curb.1  The  pavement  intervening  between 
these  gutter  courses  will  then  be  set  in  courses  at  right  angles  to  the 
axis  of  the  street,  except  in  street  intersections,  where  the  courses 
shall  make  an  angle  of  forty-five  (45)  degrees  with  the  axis  of  the 
street.  The  brick  shall  be  set  upon  edge  on  the  sand  cushion  with 
their  top  faces  parallel  to  the  pavement  datum,  in  straight  courses, 
continuous  across  the  street,  the  long  dimension  of  the  brick  being 
parallel  to  the  courses;  they  shall  be  set  as  closely  together  as  possi- 
ble, so  that  the  joints  both  between  the  courses  and  between  individ- 
ual bricks  shall  not  exceed  one-eighth  (1/8)  inch,  where  the  bricks  are 
without  lugs,  and  not  more  than  one- fourth  inch  where  the  brick 
have  lugs.  Broken  bricks  and  bats  shall  not  be  used  except  as 
closers  at  the  ends  of  the  course  and  in  fitting  the  pavement  around 
manholes,  etc.,  and  nothing  smaller  than  half -bricks  shall  be  used  in 
either  case,  and  the  broken  ends  must  be  shaped  to  make  reasonably 

1  The  object  of  this  is  to  make  a  gutter  offering  less  obstruction  to  the  flow  of 
water. 


60  STREET  ROADWA  Y  PA  VEMENTS 

close  joints.  Filling  up  with  bats  must  follow  the  brick-laying 
closely.  Brick  with  lugs  shall  be  laid  with  the  lugs  all  in  one 
direction. 

88.  Inspection. — After  the  bricks  are  laid  the  pavement  will  be 
inspected  by  the  Engineer,  or  his  agent.     He  may  require  that  the 
surface  shall  be  previously  wetted  by  sprinklers,  or  by  a  sprinkling 
nozzle,  in  order  to  detect  soft  or  porous  bricks.1     Defective  bricks 
indicated  by  him  shall  be  removed  and  replaced  by  acceptable 
brick. 

89.  Rolling  and  Ramming. — The  surface  of  the  pavement  shall 
then  be  rolled  and  rammed  in  the  following  manner: 

The  roller  used  shall  be  of  the  asphalt  roller  style,  driven  by 
steam  and  weighing  not  less  than  three  and  one-half  (3  i/  2)  nor  more 
than  five  (5)  tons.  The  rolling  shall  begin  as  near  the  curb  as 
practicable,  the  roller  being  operated  slowly,  parallel  to  the  axis 
of  the  street,  and  working  outwardly  until  the  center  of  the  street 
is  reached,  when  the  roller  will  proceed  to  the  opposite  side  of  the 
street  and  the  operation  proceed  as  before.  After  this  longitudinal 
rolling  is  completed  the  pavement  will  be  continuously  rolled  a 
second  time,  the  roller  operating  back  and  forth  at  an  angle  of 
forty-five  degrees  to  the  axis  of  the  street,  and  a  third  time,  the 
roller  operating  at  right  angles  to  the  course  of  the  second  rolling. 
After  the  rolling  is  thus  completed  the  brick  in  the  gutters  not 
reached  by  the  roller  shall  be  rammed  with  a  street  rammer  weigh- 
ing not  less  than  thirty  (30)  pounds,  a  plank  not  less  than  four  (4) 
feet  long,  ten  (10)  to  twelve  (12)  inches  wide  and  two  (2)  inches 
thick  being  interposed  between  the  pavement  and  the  rammer  and 
moved  about  so  that  the  whole  surface  of  the  gutter  shall  be  thor- 
oughly and  equally  rammed  and  its  surface  brought  to  an  even 
junction  with  the  rolled  portion  of  the  work. 

When  the  rolling  and  ramming  is  thus  completed  the  surface 
of  the  pavement  shall  conform  so  truly  to  the  designed  pavement 
datum  that  it  will  nowhere  depart  more  than  three-sixteenths  (37 16) 
inch  from  properly  formed  templates  and  straight-edges  applied  to 
its  surface. 

90.  Filling  the  Joints.2 — Directly  after  the  completion  of  the  rolling 

1  This  is  the  simplest  and  most  effective  way  to  detect  soft  and  underburned 
brick. 

2  If  the  joints  are  to  be  filled  with  bituminous  cement,  substitute  for  sections 
90  and  91  the  following: 

Directly  after  the  completion  of  the  rolling  and  ramming  all  the  joints  in  the 


BRICK  PAVEMENT  61 

and  ramming,  the  joints  between  the  bricks  shall  be  filled  as  follows: 
The  joints  in  the  longitudinal  gutter  courses,  and  the  joints 
between  six  contiguous  courses  running  across  the  street,  from 
gutter  to  gutter,  in  each  length  of  fifty  (50)  feet  of  the  pavement, 
shall  be  filled  with  bituminous  cement  composed  of  coal-tar  pitch, 
commercially  known  as  Number  Four,  to  which  has  been  added 
twenty  (20)  per  cent,  of  refined  Trinidad  asphalt  and  twenty  (20) 
per  cent,  of  hydraulic  cement,  all  by  weight.  In  preparing  this 
bituminous  cement,  the  pitch  shall  first  be  melted  and  the  asphalt, 
also  melted,  added  and  thoroughly  incorporated  by  agitation.  The 
hydraulic  cement  shall  then  be  added  and  the  whole  agitated  until 
a  complete  and  uniform  mixture  results.  The  bituminous  cement 
thus  prepared  shall  while  sufficiently  hot  and  liquid  to  flow  freely, 
be  poured  from  a  spouted  vessel  into  the  joints  until  they  appear 
to  be  nearly  or  quite  full.  After  allowing  time  for  the  filling  to 
subside,  the  joints  will  be  gone  over  a  second  time  and  completely 
filled. 

All  the  remaining  joints  in  the  pavement  shall  be  filled  with 
Portland  cement  grout,  as  follows : 

The  grout  will  be  composed  of  equal  parts  by  volume  of  sand 
(Sect.  30)  and  Portland  cement  (Sect.  29),  a  quick-setting  cement 
being  preferred.  The  sand  and  cement  shall  be  first  thoroughly 
mixed  dry  and  then  enough  water  added  to  make  a  grout  of  such 
consistency  that  it  will  flow  like  thick  cream,  and  the  mixing  con- 
tinued until  a  homogeneous  mass  is  produced  and  until  the  grout 

brick  pavement  and  between  it  and  the  curbing,  manholes  or  other  structures, 
shall  be  filled  with  a  bituminous  cement  in  the  following  manner: 

The  bituminous  cement  shall  be  composed,  by  weight,  of  one  hundred  (100) 
parts  of  straight-run  coal-tar  pitch  commercially  known  as  number  four  and 
twenty  (20)  parts  of  refined  Trinidad  asphalt  .melted  and  thoroughly  mixed  to- 
gether at  a  temperature  of  about  350°  F.,  to  which  shall  be  added  twenty  (20) 
parts  of  dry  Portland  cement,  which  shall  be  thoroughly  incorporated  with  the 
hot  bitumen  until  a  homogeneous  mass  is  produced,  and  kept  agitated  so  as  to 
prevent  settlement  or  separation  until  the  cement  is  used.  If  another  asphalt 
is  used  instead  of  Trinidad  the  quantity  added  to  the  pitch  must  be  sufficient 
so  that  the  cement  will  not  flow  at  a  temperature  lower  than  one  hundred  and 
twenty-five  degrees  Fahrenheit  (125°  F.).  This  cement  while  at  a  temperature 
of  about  325  degrees  F.  shall  then  be  poured  from  a  spouted  vessel  into  all  joints 
and  vacancies  in  the  pavement  until  they  are  completely  filled,  repouring  being 
resorted  to  if  necessary  to  accomplish  the  complete  filling  of  the  joints.  After 
the  joints  are  thus  filled  a  layer  of  sand  one-half  inch  thick  will  be  spread  over 
the  whole  surface  of  the  pavement  and  allowed  to  remain  until  the  engineer  shall 
direct  its  removal. 


62  STREET  ROADWAY  PAVEMENTS 

is  applied  to  the  pavement.  The  grout  shall  be  prepared  in  water- 
tight boxes  of  a  convenient  size.  Before  applying  the  grout  the 
pavement  shall  be  thoroughly  dampened  by  sprinkling.  The  grout 
shall  be  spread  over  the  pavement  with  scoop  shovels,  in  two 
courses,  the  first  being  sufficient  to  nearly  fill  the  joints,  and  the 
second,  which  shall  be  applied  before  the  first  has  begun  to  set, 
shall  be  sufficient  to  entirely  fill  the  remaining  space  in  the  joints. 
As  rapidly  as  the  grout  is  applied  it  shall  be  swept  with  brooms  until 
it  all  enters  the  joints.1 

91.  Travel  must  be  excluded  from  the  pavement  until  the  grout 
has  set  firmly;  in  no  case  less  than  five  days,  and  the  grout  must 
be  kept  moist  during  this  period. 


WOOD-BLOCK  PAVEMENT 

92.  Sub-grade. — The  sub-grade  for  wood-block  pavement  shall 
be  prepared  as  specified  in  Section  26,  and  shall  be  finished  to  a 
surface inches  below  the  pavement  datum. 

93.  Foundation. — The  foundation  for  wood-block  pavement  shall 
be    Portland    cement    concrete inches    thick,  pre- 
pared as  specified  in  Sections  28,  29,  30,  31,  32,  33,  34,  35,  36  and  37. 
The  upper  surface  of  the  concrete  foundation,  when  completed,  shall 
be  at  a  distance  below  the  pavement  datum  equal  to  the  depth  of 
the  blocks  to  be  laid,  plus  one-half  (1/2)  inch,  and  must  not  vary 
more  than  one-fourth  (1/4)  inch  above  or  below  that  depth. 

1  The  bituminous-cement  joints  are  principally  for  the  purpose  of  providing 
for  the  expansion  of  the  pavement  in  very  hot  weather. 

Experience  seems  to  have  proved  that  cement  grout  is,  everything  considered, 
the  best  and  cheapest  filling  for  the  joints  in  brick  pavement.  If  the  filling  is 
properly  done,  the  edges  of  the  brick  are  supported  and  the  corners  do  not  chip 
off.  With  the  expansion  joints  provided  at  intervals  by  the  bituminous-filled 
joints,  the  curbs  will  not  be  forced  out  of  line,  nor  will  the  pavement  be  raised 
from  its  sand  bed  by  expansion,  causing  the  rumbling  sound  sometimes  noticed. 

Where  grout  filling  is  used  there  seems  to  be  no  necessity  for  covering  the  surface 
of  the  pavement  with  sand,  as  is  usually  done,  provided  the  grout  is  kept  damp. 


WOOD-BLOCK  PA  VEMENT  63 

MATERIALS 

94.  Wood-blocks. — The  wood-blocks  may  be  made  of  Long- 
leaved  yellow  pine  (Pinus  palustrus),  Lob-lolly  pine  (Pinus  tseda), 
Short-leaved  pine  (Pinus  echinata),  Cuba  pine  (Pinus  heterophylla), 
Black  gum  (Nyssa  sylvatica),  Red  gum  (Liquidambar  styraciflua), 
Norway  pine  (Pinus  resinosa),  or  Tamarack  (Larix  laricina),  or  of 
other  species  of  wood  of  equal  strength  and  toughness  and  of  a 
texture  permitting  as  satisfactory  preservative  treatment  as  those 
herein  named.  But,  as  far  as  practicable,  only  one  species  of  wood 
shall  be  used  on  any  one  contract.1 

1  Since  immunity  from  early  natural  decay  is  secured  by  preservative  treat- 
ment, the  important  requisite  for  wood  paving  blocks  is  capacity  to  withstand 
the  wear  and  tear  of  the  travel  on  the  street.  We  have  as  yet  no  very  satis- 
factory data  as  to  the  ability  of  the  various  species  of  wood  to  endure  the  some- 
what peculiar  and  special  duty  to  which  paving  blocks  are  subjected. 

The  test  which  seems  to  most  nearly  approach  to  what  is  wanted  is  that  of' 
crushing  strength,  when  the  force  is  applied  to  the  end  of  the  sample,  parallel 
to  its  fibers;  but  this  does  not  embrace  the  effect  of  impact  to  which  paving 
blocks  are  subjected  under  street  travel.  Whether  this  may  be  considered  a 
function  of  the  end-crushing  strength  or  not  is  an  open  question,  though  there 
seems  good  reason  to  believe  that  it  will  prove  to  be  so;  and  if  so,  there  is  no 
good  reason  why  woods  of  substantially  equal  strength  under  the  end-crushing 
test  should  not  show  about  the  same  endurance  under  street  travel,  independent 
of  the  element  of  natural  durability,  which  is  practically  eliminated  by  preserva- 
tive treatment. 

The  end-crushing  strength  per  square  inch  of  some  of  the  kinds  of  timber  named 
as  acceptable  is  about  as  follows: 

Southern  long-leaved  yellow  pine 6900  Ibs. 

Lob-lolly   pine 6500  Ibs. 

Short-leaved  pine 5900  Ibs. 

Cuban  pine 7900  Ibs. 

Norway  pine * 6700  Ibs. 

Red  gum 7100  Ibs. 

It  was  formerly  very  customary  to  specify  that  only  Southern  long-leaved 
yellow  pine  might  be  used  for  paving  blocks,  though  this  requirement  was 
seldom  strictly  enforced.  The  fact  is,  that  with  the  exception  of  the  test  based 
upon  the  number  of  growth  rings  per  inch,  it  requires  an  expert  knowledge, 
acquired  only  by  long  experience,  to  distinguish  with  certainty  the  species  of 
Southern  pine  from  the  appearance  of  the  lumber  alone.  It  is  now  almost 
impossible  to  obtain  in  the  market  shipments  of  strictly  long-leaved  yellow  pine, 
and  while  that  wood  is  undoubtedly  superior  to  the  other  pine  timbers  for  paving 
blocks  it  seems  useless  to  specify  its  exclusive  use,  or  to  propose  specifications 
designed  to  exclude  lumber  made  from  other  species  of  pine.  It  was  doubtless 
the  recognition  of  this  situation  that  influenced  the  Association  for  Standardizing 
Paving  Specifications,  at  its  last  (New  Orleans)  convention  to  adopt  a  specifica- 


64  STREET  ROADWA  Y  PA  VEMENTS 

Only  wood  from  live,  sound  trees  shall  be  used.  The  lumber  from 
which  the  blocks  are  cut  shall  be  properly  manufactured,  free  from 
bark,  and  with  full  square  corners.  It  shall  be  free  from  decay, 
dotiness,  brashness,  shakes,  large  season  cracks,  loose  or  unsound 
knots  over  three-fourths  (3/4)  inch  in  diameter,  and  all  other  im- 
perfections which  may,  in  the  opinion  of  the  Engineer,  be  detri- 
mental. "Fat"  pine  containing  so  much  resin  that  it  will  not  take 
up  the  specified  quantity  of  creosote  oil  in  treatment  may  be  rejected. 
Second-growth  timber,  and  Southern  pine  showing,  outside  of  a 
radius  of  three  (3)  inches  from  the  heart,  nine  (9)  or  less  annual 
growth  rings  to  the  inch,  will  not  be  accepted. 

The  paving  blocks  made  from  the  lumber  hereinbefore  specified 
shall  be  well  manufactured  and  truly  rectangular  and  square  edged. 

Their  depth  (parallel  to  the  fiber)  shall  be inches,1 

their  length  shall  not  be  less  than  six  inches  nor  more  than  three 
times  their  depth,  and  their  width  shall  be  from  two  and  one-half 
(2  1/2)  to  three  and  one-half  (3  1/2)  inches,  but  at  least  one-fourth 
inch  less  than  their  depth. 

tion  which  practically  admits  everything  known  in  the  market  as  "Southern 
yellow  pine"  having  annual  growth  rings  averaging  less  than  eight  to  the  inch 
and  excluding  all  timber  having  less  than  six  rings  to  the  inch.  Within  these 
limits  these  specifications  practically  admit  all  pine  lumber  shipped  from  South- 
ern mills. 

The  specifications  here  proposed,  by  limiting  the  number  of  growth  rings  to 
nine  per  inch,  would  not  confine  the  lumber  to  true  long-leaved  yellow  pine,  but 
would  secure  a  more  mature  and  solid  quality  of  lumber.  It  is  true,  however, 
that  both  these  specifications  and  those  adopted  by  the  A.  S.  P.  C.  exclude  most 
"Cuban  pine"  lumber  which  is  very  rapid  growing,  the  growth  rings  often  num- 
bering but  three  or  four  to  the  inch,  though  the  strength  of  the  wood  from  this 
species  indicates  that  it  may  safely  be  used  for  pavement. 

1  The  question  of  the  most  economical  depth  for  wood  paving  blocks  is  as  yet 
unsettled.  In  New  York  City,  blocks  3  1/2  inches  in  depth  are  adopted  as  the 
standard  and  are  being  used  on  streets  of  the  heaviest  travel,  the  practice  of 
Berlin,  Paris  and  other  foreign  cities  being  thus  followed.  The  arguments  in 
favor  of  these  short  blocks  are  lower  first  cost,  and  that,  with  much  deeper  blocks, 
the  usual  uneven  wear  of  a  wood  pavement  will  make  it  so  rough  as  to  require 
removal  before  the  blocks  are  worn  down  so  as  to  be  split  up  and  dislodged  from 
their  places.  While  reliable  data  on  these  points  are  wanting,  it  seems  to  the 
writer  very  unwise  to  use  such  short  blocks  on  streets  of  heavy  travel,  and  he 
would  recommend  that  the  minimum  length  for  use  on  such  streets  be  4  1/2 
inches,  and  he  would  prefer  5  inches. 

On  streets  of  light  travel  a  length  of  3  1/2  inches  should  be  satisfactory. 

Recent  observations  on  heavy  travelled  streets  in  New  York  indicate  that  when 
long-leaved  yellow  pine  blocks  become  worn  down  to  a  remaining  depth  of  about 
2  1/8  inches  they  split  up  into  fine  slivers  and  the  pavement  goes  to  pieces. 


WOOD-BLOCK  PA  VEMENT  65 

All  the  blocks  for  any  one  contract  shall  be  of  the  same  standard 
depth  and  width,  and  the  individual  blocks  shall  not  vary  more 
than  one-eighth  inch  from  the  designated  depth  and  width. 

95.  Creosote  Oil.1 — The  oil  used  for  the  preservative  treatment 
of  the  paving  blocks  shall  be  coal-tar  creosote  oil,  commonly  known 
as  dead  oil  of  coal  tar,  without  admixture  or  adulteration  with  other 
oils  or  tars.   Oils  produced  or  resulting  from  the  distillation  of 
water-gas  tar,  blast-furnace  tar,  producer-tar,  lignite-tar,  petroleum- 
oil  tar,  or  wood-tar,  or,  containing  an  admixture  of  any  of  these  will 
not  be  accepted.     The  creosote  oil  shall  not  contain  more  than  five 
per  cent.  (5%)  of  tarry  matter  nor  more  than  two  per  cent.  (2%)  of 
water.     Its  specific  gravity  at  a  temperature  of  100°  F.  shall  be 
not  below  1.03  nor  above  1.08.     Not  less  than  ninety-nine  per  cent. 
(99%)  shall  be  soluble  in  hot  benzol.     It  shall  not  contain  more  than 
eight  per  cent.  (8%)  of  tar  acids.     When  two  hundred  (200)  grams 
are  subjected  to  distillation  at  gradually  increasing  temperatures, 
not  more  than  five  per  cent.  (5%  )  of  distillate  shall  distil  over  up 
to  a  temperature  of  four  hundred  degrees  F.  (400°  F.),  nor  more 
than  thirty-five  per  cent.  (35%)  shall  distil  over  up  to  a  temperature 
of  four  hundred  and  fifty-five  degrees  F.  (455°  F.),  and  not  more 
than  eighty  per  cent.  (80%)  shall  distil  over  up  to  a  temperature  of 
six  hundred  degrees  F.  (600°  F.).     After  complete  distillation  there 
shall  not  remain  more  than  two  per  cent,  of  coke.     The  residue 
remaining,  upon  sulphonating  a  portion  of  the  total  distillate,  shall 
not  exceed  one  per  cent.  (i%).     The  above  tests  shall  be  made  in 
accordance  with  the  methods  prescribed   in  the  "Report  of  the 
Committee  on  Preservative  Treatment  of  Poles  and  Cross-arms" 
of  the  National  Electric  Light  Association,  1911. 

96.  Preservative   Treatment. — The   paving   blocks   shall,    after 

1  Most  of  the  more  recent  specifications  require  the  use  of  a  heavy  oil,  said  to 
be  composed  of  creosote  oil  with  an  admixture  of  refined  tar,  on  the  ground  that 
the  tar  is  necessary  as  a  water-proofing  agent  to  prevent  the  creosote  oil  from 
being  dissolved  out  by  water  or  evaporated  into  the  air.  It  is  claimed  that  if 
moisture  can  thus  be  excluded  from  entering  the  wood,  decay  will  be  prevented, 
even  in  the  absence  of  the  antiseptic  elements  of  creosote  oil.  It  is  not  intended 
to  discuss  this  matter  at  length  here.  We  know  from  long  experience  that 
genuine  creosote  oil  is  the  best  preservative  of  wood  so  far  found;  also  that  creo- 
soted  piles  have  stood  in  tidal  waters,  alternately  exposed  to  water  and  air,  for 
twenty-five  years  and  still  retain  sufficient  creosote  oil  to  resist  the  Teredo — a 
very  severe  test.  Why  experiment  with  a  comparatively  untried  material, 
particularly  when  it  costs  as  much  as  the  genuine  creosote  oil,  is  rather  more 
difficult  to  force  into  the  wood,  and  has  some  admitted  objectionable  qualities? 


66  STREET  ROADWA  Y  PA  VEMENTS 

they  are  cut  to  the  proper  dimensions,  be  subjected  to  preservative 
treatment  with  the  creosote  oil  specified  in  Section  95. 

The  contractor  may  employ  any  of  the  standard  methods  in 
common  use  for  impregnating  the  blocks,  provided  that  uniform 
results  are  attained,  complying  with  the  following  requirements: 

The  wood  shall  not  be  heated  during  any  part  of  the  process  to  a 
temperature  exceeding  two  hundred  and  sixty  degrees  Fahrenheit 
(260°  F.). 

All  parts  of  every  block  shall  be  reached  and  penetrated  by  the  oil. 
The  quantity  of  oil  found  in  the  blocks  after  treatment  shall  average 
not  less  than pounds  per  cubic  foot  of  wood. 

The  oil  in  the  treating  tanks  during  the  process  of  impregnation 
shall  not  become  diluted  with  water  to  the  extent  of  more  than  five 
per  cent.  (5%)  and  if  the  percentage  of  water  in  the  oil  during  the 
process  of  treatment  shall  exceed  two  per  cent.  (2%)  the  quantity 
of  the  oil  to  be  injected  in  the  wood  as  stipulated  hereinbefore  shall 
be  increased  in  a  like  ratio;  for  example,  if  the  oil  in  the  treating 
tanks  shall  be  found  to  contain  four  per  cent.  (4%)  of  water  the 
quantity  required  to  be  found  in  the  blocks  after  treatment  shall  be 
four  per  .cent.  (4%)  greater  than  herein  specified. 

The  quantity  of  oil  injected  shall  be  determined  primarily  by 
tank  measurements,  but  shall  be  verified  by  actual  determination 
of  the  quantity  of  oil  in  the  treated  blocks  by  the  following  method : 
representative  treated  sample  blocks  shall  be  selected  and  an  auger 
hole  one  inch  in  diameter  bored  entirely  through  the  block  parallel 
to  the  fiber,  the  borings  all  collected,  thoroughly  mixed,  and  the 
quantity  and  ratio  of  oil  to  wood  in  the  borings  determined  by 
extracting  the  oil  completely  with  carbon  disulphide.  The  center 
of  the  auger  hole  shall  be  located  midway  between  the  sides  of  the 
block  and  at  a  distance  from  the  end  of  the  block  equal  to  one-third 
(i/  3)  of  the  length  of  the  block.  At  the  time  of  treatment  the  blocks 
shall  not  be  green  or  saturated  with  water,  but  they  shall,  preferably, 
not  be  thoroughly  seasoned.  After  treatment,  and  until  used,  the 
blocks  shall,  during  dry  weather,  be  frequently  well  drenched 
with  water  to  prevent  excessive  drying  out  and  cracking 

97.  Laying  the  Wood  Blocks. — The  concrete  foundation  shall  be 
cleaned  and  swept  to  remove  all  dirt  and  debris  and  shall  be  thor- 
oughly dampened  immediately  in  advance  of  the  setting  of  the 
blocks.  Upon  the  concrete  foundation  shall  be  spread  a  layer  of 
mortar  about  one-half  inch  thick,  made  of  one  part  Portland  cement 
and  two  parts  sand  with  sufficient  water  to  make  a  moderately  stiff 


WOOD-BLOCK  PA  VEMENT  67 

paste.1  The  mortar  shall  be  thoroughly  mixed  and  shall  be  spread 
in  place  over  the  concrete  foundation  immediately  in  advance  of 
setting  the  blocks  to  such  a  thickness  that  when  the  blocks  are  set 
and  properly  tamped  their  tops  shall  conform  accurately  to  the 
pavement  datum. 

Upon  this  mortar  bed  the  blocks  shall  be  set  with  their  fiber 
vertical,  in  straight,  parallel  courses  at  right  angles  to  the  axis  of 
the  street,  except  at  street  intersections  where  they  shall  be  set  at  an 
angle  of  forty-five  degrees  with  the  axis  of  the  street.  The  blocks 
shall  be  set  as  close  together  as  practicable.  Blocks  in  adjoining 
courses  shall  break  joint  at  least  three  inches.  Blocks  of  such  lengths 
shall  be  selected  as  to  make  as  little  splitting  as  practicable  in  filling 
out  ends  of  courses.  Where  splitting  is  necessary,  no  fractional 
block  shall  be  used  whose  length  is  not  at  least  equal  to  its  width. 

After  the  blocks  are  thus  set  the  whole  surface  of  the  pavement 
shall  be  rammed  with  a  rammer  weighing  not  less  than  twenty 
pounds,  a  plank  ten  (10)  inches  wide,  two  (2)  inches  thick  and  four 
feet  long  being  interposed  between  the  rammer  and  the  pavement 
and  moved  about  as  the  ramming  progresses  until  the  blocks  are 
forced  into  a  firm  seat  in  the  mortar  bed  and  their  tops  brought 
accurately  to  the  pavement  datum.  The  ramming  shall  be  com- 
pleted before  the  mortar  under  them  has  begun  to  set,  but  no  ram- 
ming shall  be  done,  during  the  progress  of  the  work,  nearer  than  three 
feet  to  the  edge  of  the  block-setting,  except  where  the  block-setting 
may  be  suspended,  as  at  the  end  of  the  day's  work,  when  all  the 
blocks  then  set  shall  be  rammed. 

The  top  surface  of  the  pavement  when  completed  shall  conform  so 
truly  to  the  pavement  datum  that  correctly  formed  templates  twelve 
(12)  feet  long  applied  to  the  surface  shall  show  at  no  place  a  depar- 
ture of  more  than  three-sixteenths  (3/16)  inch  therefrom. 

1  It  is  a  common  practice  of  contractors  in  some  cities,  in  the  laying  of  both 
wood-block  and  asphalt-block  pavement,  where  a  mortar  bed  is  called  for,  to 
substitute  a  bed  of  mixed  sand  and  cement,  dampened  only  to  such  a  degree  as 
will  make  the  mass  pulverulent  like  damp  sand,  the  claim  being  made  that  ordi- 
nary mortar  cannot  be  spread  and  gaged  properly.  This  claim  is  unfounded. 
The  objection  to  the  practice  is  that  the  dampened  mixture  does  not  contain 
sufficient  water  to  cause  the  cement  to  set,  and  with  the  practically  water-tight 
paving  surface,  does  not  receive,  even  in  rainy  weather,  the  necessary  amount  of 
water.  If  the  weather  be  dry,  the  small  quantity  of  moisture  in  the  mixture 
quickly  evaporates,  leaving  the  so-called  mortar  bed  not  much  better  than  a 
layer  of  sand  alone.  The  writer  has  found  such  alleged  mortar  dry  and  unset 
two  weeks  after  the  pavement  had  been  completed.  If  real  mortar  is  not  to  be 
used,  a  layer  of  sand  might  almost  as  well  be  substituted  at  first. 


68  STREET  ROADWA  Y  PA  VEMENTS 

98.  Filling  the  Joints. — After  the  block  setting  is  completed, 
perfectly  dry,  fine  sand  shall  be  spread  over  the  pavement  surface 
and  swept  about  until  every  joint  into  which  the  sand  will  pene- 
trate shall  be  completely  filled.     The  remaining  sand  shall  be  left 
upon  the  pavement  for  such  time  as  the  Engineer  may  direct,  when 
it  shall  be  removed  by  the  Contractor.1 

99.  Inspection. — The  lumber  for  paving  blocks  will  be  inspected 
before  it  is  cut  into  blocks.     The  blocks  will  also  be  inspected 
upon  delivery  to  the  street  and  as  they  are  laid.     Blocks  that  have, 
in  treatment  or  subsequent  handling,  developed  open  season  cracks 
or  wind  shakes  or  other  imperfections  that  may  prevent  their  dura- 
bility or  usefulness  in  the  pavement  shall  be  rejected  and  removed 
from  the  street. 

100.  Chamfered  Blocks. — Where  wood-block  pavement  is  laid 
on  streets  or  parts  of  streets  having  a  gradient  of  more  than  3%, 
the  blocks  shall  not  be  less  than  four  (4)  inches  long,  and  the  upper 
side-corners  of  the  blocks  shall  be  chamfered  to  a  depth  of  three- 
eighths  (3/8)  inch,  the  chamfered  surface  to  make  an  angle  of  40 
degrees  with  the  vertical  sides  of  the  blocks;  or  such  other  con- 
struction shall  be  used  as  will,  in  the  opinion  of  the  Engineer,  provide 
an  equally  good  foot-hold  for  horses. 

101.  Expansion  Joints. — Before  the  blocks  are  set  there  shall 
be  placed  along  and  against  each  curb  a  board  of  tropezoida"!  section 
having  a  width  one'  inch  greater  than  the  depth  of  the  blocks,  the 
upper  edge  of  which  shall  have  a  thickness  of  three-eighths  (3/8) 
inch  for  each  ten  feet  or  fraction  thereof  of  the  width  of  the  street 
between  curbs,   and  a  bottom  width  one-fourth   (1/4)   inch  less 
than  the  top.     The  paving  blocks  at  the  beginning  and  end  of 
each  course  shall  be  set  against  this  board.     After  the  ramming 

of  the  blocks  has  been  completed,  these  boards  shall  be  carefully 

> 

1  In  a  number  of  cities  the  specifications  require  the  joints  in  wood-block  pave- 
ment to  be  filled  with  Portland  cement  grout.  If  the  blocks  are  set  as  closely 
together  as  they  should  be,  the  joints  will  be  so  narrow  that  no  grout,  thick  enough 
in  consistency  to  be  of  value,  will  enter  them,  except  for  a  short  distance  down 
from  the  top,  the  remaining  depth  of  the  joints  remaining  unfilled.  An  examin- 
ation of  any  well-laid  wood-block  pavement  soon  after  it  has  been  attempted  to 
fill  the  joints  with  grout  will  verify  this  statement.  Furthermore,  the  oil  which 
exudes  from  the  blocks,  acting  on  the  thin  films  of  grout,  seems  to  deteri- 
oriate  the  mortar  and  to  render  it  practically  inert.  On  the  contrary,  fine 
dry  sand  will  readily  run  into  and  completely  fill  the  joints,  and  under  travel 
the  joints  will  soon  become  impervious  to  water.  The  sand  filling  is  therefore 
regarded  as  better,  and  it  costs  less  than  the  grout  filling. 


BITUMINOUS  CONCRETE  PA  VEMENT  69 

withdrawn  and  the  space  between  the  curbs  and  the  paving  blocks 
shall  be  completely  filled  with  the  bituminous  paving  cement 
described  in  Section  90. 

1 02.  The  street  shall  not  be  opened  to  travel  until  such  time  as 
the  mortar  under  the  blocks  shall  have  become  well  set,  nor  until 
the  Engineer  shall  so  direct. 


BITUMINOUS  CONCRETE  PAVEMENT 

Note. — The  phrase,  Bituminous  Concrete  Pavement,  has  been  applied 
to  a  large  variety  of  roadway  surfaces  differing  materially  from  each  other 
in  composition,  construction  and  utility.  Some  of  these  are  covered  by 
United  States  patents,  the  scope  and  limitations  of  which  are  not  yet  fully 
determined  or  understood.  The  necessity  of  avoiding  infringement  of 
these  patents  has  to  be  kept  in  mind  in  framing  specifications  for  public 
use,  and  this  consideration  does  not  permit  the  presentation  here  of  speci- 
fications which,  in  the  opinion  of  the  author,  would  secure  an  ideal  pavement 
of  this  general  character. 

Bituminous  concrete  pavements  constructed  in  substantial  conformity 
with  these  specifications  have  been  laid  on  a  number  of  city  and  town 
streets  and  country  roads  and  have  proved  satisfactory  and  fairly  durable 
in  use.  It  is  believed  that  they  do  not  infringe  any  existing  patents. 

Our  rather  limited  experience  with  pavements  of  this  character  seems  to 
indicate  that  if  good  materials  are  used  and  the  work  properly  done,  they 
are  suitable  for  use  on  city  streets  of  light  travel,  and  on  suburban  streets 
and  country  roads  carrying  an  amount  of  travel  considered  heavy  for 
these  classes  of  roadways.  Where  the  results  have  been  unsatisfactory, 
the  cause  can  generally  be  traced  to  unsuitable  materials  or  unskillful 
construction,  the  result  of  ignorance  or  carelessness  on  the  one  hand,  or  of 
the  attempt  to  reduce  first  cost  below  normal  figures  on  the  other.  Many 
people  are  searching  for  a  pavement  or  roadway  that  will  have  all  the  good 
qualities  of  the  standard  pavements  but  can  be  built  about  as  cheaply  as 
a  common  macadam  road.  It  is  possible  that  something  of  the  kind  may 
be  discovered;  but  in  the  present  state  of  the  art  it  is  chimerical.  High 
quality  and  low  first  cost  do  not  go  together  in  street  paving.  The 
question  to  be  considered  is,  rather,  how  can  we  invest  a  dollar  in  street 
or  road  building  so  that  it  will,  in  the  long  run,  yield  the  best  return  upon 
the  investment.  The  pavement  provided  for  in  these  specifications  is 
not  a  cheap  pavement,  but  where  it  is  suitable  for  the  conditions  to  be 
met,  it  will  be  well  worth  its  cost. 


70  STREET  ROADWAY  PAVEMENTS 

SPECIFICATIONS 

103.  Sub-grade. — The  sub-grade  except  where  old  pavement  is 
utilized  for  foundation  shall  be  prepared  in  accordance  with  Section 
26  of  these  general  specifications. 

104.  Foundation.1 — The    foundation    for    bituminous    concrete 
pavement  shall  be  a  properly  prepared  old  pavement,  or  hydraulic 
concrete,  or  compressed  broken  stone,  as  determined  by  the  engineer. 

105.  Old  macadam  pavement  or  road  to  be  utilized  for  foundation, 
shall  be  prepared  in  the  following  manner: 

All  high  places  or  humps  shall  be  dressed  down  to  a  plane  two  (2) 
inches  below  the  pavement  datum,  the  work  being  done  with  care 
so  as  to  disturb  as  little  as  possible  the  macadam  that  is  to  remain. 
Depressions  in  the  old  macadam  shall  be  carefully  cleaned  out  so 
as  to  remove  all  earth  and  other  debris  and  loose  material,  and 
filled  with  hydraulic  concrete.  Newly  dug  or  filled  trenches  and 
holes  extending  through  the  macadam  shall  be  excavated  and 
cleaned  out  so  as  to  admit  the  use  of  at  least  four  (4)  inches  of 
hydraulic  concrete.  The  hydraulic  concrete  for  thus  leveling 
up  the  roadway  shall  be  composed  of  one  (i)  part  of  approved 
Portland  cement,  four  (4)  parts  of  clean  sand  and  nine  (9)  parts 
of  sound,  hard  crushed  stone,  well  mixed  into  a  wet  concrete.  After 
placing,  the  concrete  shall  be  well  tamped  so  as  to  form  a  compact 
body,  conforming  to  a  plane  two  (2)  inches  below  the  pavement 
datum.  The  concrete  shall  be  protected  from  travel  and  allowed 
to  become  well  set  before  the  surface  of  bituminous  concrete  is 
applied. 

1 06.  Old  stone-block  or  brick  pavement   may  be  utilized  for 
foundation,  provided  that  the  blocks  or  bricks  do  not  require  to 

1  Wherever  an  old  pavement  or  macadam  road  can  be  utilized  it  makes  an 
excellent  foundation  for  a  pavement  of  this  kind,  provided  it  is  not  in  too  dilapi- 
dated a  condition,  extends  from  curb  to  curb,  and  its  surface  conforms  near 
enough  to  the  desired  street  surface  so  that  the  necessary  changes  and  repairs 
will  not  be  too  expensive.  Where  the  new  pavement  is  expected  to  carry  quite 
a  heavy  travel  it  is  not  advisable  to  use  plain  crushed  stone  for  filling  depressions 
and  leveling  up  the  surface.  It  is  difficult,  even  where  proper  care  is  used,  to 
make  such  patches  of  broken  stone  as  firm  and  strong  as  the  adjoining  old  pave- 
ment, which  is  a  necessary  condition  to  secure  satisfactory  results;  for  if  the 
masses  of  broken  stone  yield  under  travel,  slight  depressions  will  form  over 
them  in  the  bituminous  surface,  which  will  in  time  become  holes  requiring 
repairs.  The  1:4:9  concrete  specified  for  this  work  is  not  very  much  more 
expensive  than  plain  broken  stone,  it  will  not  shift  or  break  up  under  travel, 
and  will  in  the  end  prove  a  better  investment. 


BITUMINOUS  CONCRETE  PA  VEMENT  7 1 

be  taken  up  and  reset,  or,  if  so  taken  up  and  reset,  that  the  joints 
shall  be  completely  filled  with  grout  composed  of  one  (i)  part  Port- 
land cement  and  two  (2)  parts  of  good  sand.  Depressions,  trenches 
and  holes  shall  be  treated  as  specified  in  Section  105. 

107.  Hydraulic  concrete  foundation  shall  be  constructed  in  com- 
pliance with  the  requirements  of  Sections  28,  29,  30,  31,  32,  33, 
34  ?  35>  S^  and  37  of  these  specifications.     Its  depth  or  thickness 
shall  be inches. 

108.  Broken  stone  foundation  shall  be inches  in 

thickness  after  completion.     It  shall  be  constructed  in  accordance 
with  Section  40  of  these  specifications.1 

109.  When  completed  the  upper  surface  of  the  foundation  shall 
nowhere  be  more  than  two  and  one-half  (2  1/2)  inches  nor  less 
than  one  and  three-fourths  (i  3/4)  inches  below  the  pavement  datum. 
No  travel  shall  be  permitted  upon  the  foundation  until  the  bitumin- 
ous concrete  shall  have  been  laid. 

no.  Bituminous  Concrete. — The  bituminous  concrete  shall  be 
composed  of  crushed  stone,  sand,  pulverized  stone,  and  asphaltic 
cement. 

A  typical  composition  for  the  bituminous  concrete,  to  be  as 
closely  approximated  as  practicable,  is  as  follows,  the  percentages 
being  by  weight: 

1  Where  a  new  foundation  is  required  broken  stone  or  macadam  is  most  fre- 
quently used  for  bituminous  concrete  pavements.  Unless  such  foundations  are 
constructed  in  the  same  way  and  with  about  the  same  care  as  is  necessary  for 
a  macadam  road  it  is  liable  to  prove  unsatisfactory.  Under  the  very  heavy 
wheel  loads  that  may  occasionally  pass  over  the  streets,  imperfectly  compacted 
broken  stone  is  likely  to  shift  sufficiently  to  start  incipient  ruts  which  will  enlarge 
and  in  time  necessitate  expensive  repairs.  Such  conditions  are  frequently  seen 
on  bituminous  concrete  pavements  subjected  to  heavy  travel.  These  pave- 
ments, like  sheet  asphalt  pavements,  require  a  foundation  that  will  be  absolutely 
unyielding  under  travel.  For  this  reason  a  concrete  foundation  will  generally 
be  found  more  economical  in  the  long  run  than  a  broken  stone  foundation.  The 
increased  first  cost  per  square  yard  is  not  very  great  and  this  additional  money 
will  in  most  cases  prove  a  good  investment.  At  the  usual  prices  of  material  and 
labor  a  square  yard  of  4  inch  concrete  should  cost  about  50  cents,  while  a  properly 
constructed  broken  stone  foundation  6  inches  thick  (which  would  not  nearly 
equal  in  strength  and  rigidity  4  inches  of  concrete)  would  cost  about  45  cents 
per  square  yard.  Considering  the  much  greater  durability  and  lower  cost  of 
repairs  of  the  pavement  on  the  concrete  foundation,  this  small  additional  cost 
is  not  worth  consideration.  While  the  specifications  are  made  to  cover  the  three 
kinds  of  foundation,  it  is  assumed  that  the  kind  of  foundation  to  be  used  will 
be  decided  in  advance,  and  that  the  part  of  these  specifications  relating  to  the 
others  kinds  of  foundation  will,  in  actual  use  be  omitted. 


72  STREET  ROA  DWA  Y  PA  VEMENTS 

Pure  bitumen  in  asphaltic  cement 8.5% 

Pulverized  stone  passing  No.  200  sieve 8.5% 

Sand  passing  No.  80  sieve 10.0% 

Sand  passing  No.  40  sieve 23 .  o% 

Sand  and  fine  stone  passing  No.  10  sieve 15.0% 

Crushed  stone  passing  a  screen  having  four  meshes 

to  the  linear  inch 25 . o% 

Crushed  stone  passing  a  screen  having  two  meshes 

to  the  linear  inch 10 .  o% 

100.0% 

The  crushed  stone  shall  be  trap-rock,- granite  or  hard,  sound, 
durable  limestone.  It  shall  be  crushed  to  such  sizes  that  all  will 
pass  through  a  screen  with  two  meshes  to  the  linear  inch  and  shall 
be  of  such  assorted  sizes  of  fragments  as  will,  when  incorporated  with 
the  sand,  pulverized  stone,  and  bitumen,  produce  a  mixture  sub- 
stantially conforming  to  the  percentages  of  each  named  in  the 
preceding  paragraph. 

The  stone  shall  be  freshly  crushed,  clean  and  free  from  clay,  loam, 
organic  matter  and  refuse  of  every  kind. 

The  sand  shall  be  silicious,  and  free  from  clay,  loam  and  refuse 
of  all  kinds.  The  grains  shall  be  of  such  sizes  that  approximately 
twenty-five  per  cent.  (25%)  of  the  whole  will  pass  the  number 
eighty  (80)  sieve,  fifty-eight  per  cent.  (58%)  shall  pass  the  No.  40 
sieve  and  not  more  than  seventeen  per  cent.  (17%)  will  pass  the 
number  10  sieve,  when  used  in  the  order  named.  The  pulverized 
stone  shall  conform  to  the  requirements  of  Sect.  49.  Portland 
Cement  may  be  substituted  for  not  more  than  twenty  per  cent. 
(20%)  of  the  pulverized  stone  if  the  Engineer  so  directs,  in  which 
case  the  Portland  Cement  actually  so  used  shall  be  paid  for  extra 
at  the  prevailing  market  price,  to  be  agreed  upon  in  advance.  The 
asphaltic  cement  shall  comply  with  the  requirements  of  Sects.  43,  44, 
45,  46,  47,  and  50,  except  that  it  may  have  a  somewhat  higher 
penetration,  as  may  be  determined  by  the  Engineer.1 

1  A  bituminous  cement  composed  largely  of  coal-tar  pitch  has  heretofore  been 
most  used  in  pavements  of  this  character.  It  is  not  denied  that  very  good 
pavements  have  been,  and  can  be  built  with  this  material,  but  the  superiority 
of  the  asphaltic  cement  here  specified  is  so  great  that  it  is  true  economy  to  use  it. 
The  difference  in  cost  at  prevailing  prices  of  material  will  be  ten  to  twelve  cents 
per  square  yard.  The  greater  durability  and  serviceability  of  the  pavement 
made  with  the  asphaltic  cement  will,  particularly  on  streets  of  comparatively 
heavy  travel,  far  more  than  justify  this  additional  cost. 


HYDRA  ULIC  CONCRETE  ROADWA  Y  PA  VEMENT      73 

in.  Mixing. — The  materials  composing  the  concrete  shall  all 
(except  the  pulverized  stone  and  Portland  cement)  be  uniformly 
heated  to  a  temperature  not  exceeding  three  hundred  and  fifty 
degrees  Fahrenheit  (350°  F.)  and  not  below  three  hundred  degrees 
Fahrenheit  (300°  F.),  and  while  at  such  temperature  shall  be 
incorporated  and  mixed  in  a  mechanical  mixer.  The  stone,  sand, 
and  pulverized  stone  shall  be  placed  in  the  mixer  in  the  order  named 
and  well  mixed  together,  after  which  the  asphaltic  cement  shall  be 
added  and  the  mixing  continued  until  each  fragment  is  thoroughly 
coated  with  cement. 

112.  Laying  on  the  Street. — The  mixed  concrete  shall  be  taken  to 
the  street  as  soon  as  practicable  after  leaving  the  mixer.  It  shall  be 
unloaded  on  the  street,  properly  spread  and  truly  graded  with 
asphalt  rakes  to  such  a  depth  that  after  compression  by  rolling  it  will 
have  a  thickness  of  not  less  than  two  inches.  The  concrete  when 
unloaded  on  the  street  shall  be  at  a  temperature  not  below  two 
hundred  and  eighty  degrees  Fahrenheit  (280°  F.).  In  spreading 
and  grading,  all  material  must  be  moved  from  the  pile  into  which 
it  was  unloaded.  As  soon  as  practicable  after  the  concrete  shall 
be  graded,  the  surface  shall  be  thoroughly  rolled  with  a  ten-ton 
asphalt  roller  and  the  rolling  continued  until  the  roller  makes  no 
further  impression  on  the  concrete  surface.  When  completed  the 
surface  must  conform  closely  to  the  pavement  datum  so  that  there 
will  be  no  depressions  or  elevations  exceeding  one-fourth  inch  above 
or  below  the  pavement  datum. 


HYDRAULIC  CONCRETE  ROADWAY  PAVEMENT1 

113.  The  sub-foundation  for  hydraulic  concrete  pavement  shall 
be  prepared  as  specified  in  Section  26. 

1  Hydraulic  concrete  pavement  is  to  be  recommended  only  for  country  road- 
ways and  for  city  streets  of  very  moderate  travel.  While  our  experience  with 
this  kind  of  pavement  is  yet  limited  there  is  reason  to  believe  from  the  nature 
of  the  material  that  it  will  not  prove  to  be  a  satisfactory  or  economical  pavement 
for  streets  of  heavy  travel.  But  in  all  cities  and  towns  there  are  many  residence 
streets  where  the  travel  is  very  light,  and  yet  where  a  permanent  pavement 


74  STREET  ROADWAY  PAVEMENTS 

114.  The  pavement  shall  be  constructed  in  two  courses  called 
the  bottom  course  and  the  top  course,  as  hereinafter  specified.1 

115.  Bottom   Course. — The   bottom    course   shall   be   four    (4) 
inches  in  thickness2  and  shall  be  composed  of  the  materials  speci- 
fied in  Sects.  29,  30,  and  31.     The  concrete  shall  be  composed  of 
one  part  Portland  cement,  three  parts  sand  and  six  parts  of  broken 
stone,  and  shall  be  mixed  and  placed  as  specified  in  Sects.  35  and  36, 
but  its  top  surface  when  properly  compacted  shall  be  parallel  to 
and  not  less  than  two  (2)  nor  more  than  two  and  one-half  (2  1/2) 
inches  below  the  pavement  datum. 

116.  Top  or  Surface  Course. — The  top  course  shall  be  composed 
of  the  Portland  cement  specified  in  Sect.  29,  the  sand  specified  in 
Sect.  30  except  that  it  shall   be  especially  clean,  and  the  grains 
shall  be  of  such  size  that  at  least  seventy-five  per  cent.  (75%)  of 
the  mass  will  fail  to  pass  a  screen  having  thirty  (30)  meshes  to  the 

is  wanted  and  warranted.  For  these,  it  is  believed  that  a  properly  constructed 
concrete  pavement  will  prove  very  satisfactory  and  durable,  and  the  low  cost 
at  which  it  can  be  constructed  should  make  it  very  attractive  to  city  officials  and 
property  owners.  The  author  has  advocated  its  use -under  such  conditions 
for  many  years  (see  Engineering  News,  July  2ist,  1904).  Like  other  composite 
pavements  its  utility  and  durability  will  depend  largely  upon  the  good  quality 
of  the  materials  used  and  the  skill  and  thoroughness  with  which  the  work  is 
done. 

The  specifications  here  offered  are  the  result  of  the  observation  and  experience 
of  the  author,  and  it  is  believed  that  pavements  laid  in  accordance  with  them  will 
give  very  satisfactory  results. 

1  A  number  of  engineers  advocate  the  construction  of  concrete  pavement  in 
one  homogeneous  course,  and  quite  a  number  of  pavements  have  been  con- 
structed in  this  way. 

Like  any  other  composite  pavement,  it  is  called  upon  to  perform  two  functions; 
to  safely  sustain  the  weight  of  loads  passing  over  it,  and  to  resist  wear  and 
abrasion  of  its  surface.  A  material  and  form  of  construction  that  meets  the 
first  requirement  may  not  meet  the  second.  Experience  has  proved  that  ordi- 
nary 1:3:6  concrete  makes  an  entirely  satisfactory  foundation  for  any  pave- 
ment, but  it  lacks  the  hardness  and  strength  to  successfully  resist  the  surface 
abrasion  of  travel.  To  secure  this  quality  a  richer  and  harder  concrete  is  called 
for,  but  it  is  unnecessary  that  the  foundation  should  be  equally  hard.  To 
construct  the  pavement  in  two  courses  as  here  specified  would  seem  to  be  the 
logical  way,  especially  as  it  decreases  the  total  cost,  and  should  make  a  more 
durable  pavement. 

2  Some  engineers  advocate  a  greater  total  thickness  of  the  pavement  than  is 
here  specified  (6  inches).     Considering  that  this  pavement  should  never  be  used 
on  heavy  traveled  streets,  a  total  thickness  of  concrete  of  six  inches  will  have 
ample  strength  to  carry  the  loads  to  which  it  will  be  subjected.     If  so,  it  is  a 
useless  waste  of  money  to  increase  the  thickness  of  the  concrete. 


HYDRAULIC  CONCRETE  ROADWAY  PAVEMENT      75 

linear  inch,  and  shall  be  of  superior  quality  for  making  concrete; 
and  of  crushed  Trap  Rock,1  or  of  stone  equally  hard,  strong  and 
durable. 

The  trap  rock  shall  be  crushed  to  such  sizes  that  all  will  pass 
through  a  screen  having  meshes  one  and  one-fourth  (i  1/4)  inch 
square  and  that  none  will  pass  through  a  screen  having  meshes 
one-half  (1/2)  inch  square,2  and  it  shall  be  free  from  clay,  refuse  or 
other  foreign  substances. 

117.  The  surface-course  concrete  shall  be  composed  of  one  part 
Portland  cement  complying  with  Sect.  29,  one  and  three  quar- 
ters (i  3/4)  parts  of  sand,  and,  generally,  three  and  one-half 
(3  1/2)  parts  of  crushed  stone,  but  the  ratio  of  crushed  stone  shall 
be  such  that  in  the  completed  concrete  the  volume  of  mortar  in 
the  compressed  mass  shall  exceed  by  about  fifteen  per  cent.  (15%) 
the  voids  in  the  stone.3  The  cement  and  sand  shall  be  thoroughly 
mixed  together  dry,  enough  clean  water  then  added  to  make  a 
rather  wet  mortar  and  the  mixing  continued  until  the  materials 
are  thoroughly  incorporated  into  a  homogeneous  mass.  The  crushed 
stone  shall  then  be  added,  and  the  mixing  continued  until  every 
fragment  of  stone  is  completely  covered  with  mottar.  Sufficient 
water  shall  be  added  during  the  mixing,  if  necessary,  to  make  a 
"wet"  concrete,  but  not  so  wet  that  free  water  will  flow  from  the 
mixed  mass.  In  handling  and  adding  the  stone  to  the  mortar 
care  must  be  taken  to  prevent  the  stone  segregating  into  masses 
of  different  sizes.  The  concrete  for  the  top  course  shall  be  made 


1  The  use  of  limestone  for  the  top  course  (unless  it  is  of  very  superior  quality) 
is  not  advisable  or  economical  unless  the  cost  of  trap  rock  is  so  high  as  to  be 
prohibitive,  which,  considering  its  superior  durability  under  the  wear  of  travel, 
will  not  often  be  the  case. 

2  It  is  advisable  to  remove  the  screenings  from  this  surface  mixture  for  two 
reasons:  first,  to  secure  greater  uniformity  of  composition.     If  the  screenings 
are  allowed  to  remain  in  the  aggregate,  there  is  danger  of  segregation  into  patches 
of  different  sized  aggregate  and  different  ratios  of  materials,  which  it  is  very 
important  to  avoid,  and  second,  the  small  fragments  of  stone  are  more  likely 
to  be  crushed  under  the  concentrated  weight  of  wheels  than  the  larger  masses, 
and  to  thus  start  disintegration.    Lack  of  uniformity  in  the  composition  and 
homogeniety  in  this  surface  course  concrete  is  especially  to  be  guarded  against, 
otherwise  the  surface  of  the  pavement  will  wear  unevenly  and  depressions  and 
ruts  are  likely  to  result. 

3  The  ideal  composition  of  this  surface-course  concrete  is  one  where  the  stone 
forms  the  largest  possible  part  of  the  mass  consistent  with  sufficient  mortar  to  fill 
the  voids  and  thoroughly  bind  the  fragments  of  stone  together. 


76  STREET  ROADWA  Y  PA  VEMENTS 

with  special  care  and  thorough  work,  the  intention  being  to  secure 
a  superior  quality  of  concrete.1 

118.  The  concrete  thus  prepared  shall  be  placed  upon  the  bottom 
course  before  the  latter  has  begun  to  set2  and  carefully  graded 
so  that  when  properly  compacted  its  top  surface  will  coincide  with 
the  pavement  datum.     The  concrete  will  then  be  well  rammed  by 
rammers  having  a  face  of  6  by  6  inches  and  weighing  not  less  than 
twenty  (20)  pounds  after  which  the  surface  will  be  completed  by 
rolling  with  a  power  roller  of  the  asphalt  type  weighing  not  less  than 
five  (5)  tons.3     All  these  operations  must  be  completed  before  any  of 
the  concrete  in  either  course  shall  have  begun  to  set.     The  surface 
shall  not  be  plastered  with  neat  mortar  nor  shall  it  be  trowelled. 

119.  The  completed  surface  must  coincide  with  the  pavement 
datum  to  the  extent  that  a  properly  formed  template  when  applied 
to  the  surface  shall  show  no  departure  from  the  pavement  datum 
exceeding  three-sixteenths  (3/16)  inch. 

1 20.  After  the  laying  of  the  pavement  has  been  completed  it 
shall  be  allowed  to  stand  until  the  concrete  of  both  courses  shall  be 
fully  set,  which  period  shall  be  not  less  than  ten  (10  days),  or  longer,  if 
conditions  make  a  longer  time  necessary,  as  the  engineer  may  direct, 
of  which  he  shall  be  the  sole  judge.     During  this  period  the  concrete 
shall  be  kept  in  a  moist  condition  throughout,  by  sprinkling  with 
hose  or  otherwise.     No  travel  shall  be  allowed  upon  the  street  until 
the  engineer  shall  open  it  for  public  use.     The  concrete  shall  not 
be  laid  during  rain  storms  or  when  the  thermometer  is  below  forty- 
five  (45)  degrees  F.,  and  in  case  there  may  be  danger  from  frost  the 
whole  surface  of  the  concrete  shall  be  covered  by  straw  or  hay. 
Manure  must  not  be  used  for  this  purpose. 

121.  Expansion  Joints.4 — An  expansion  joint  along  the  curbing  on 
each  side  of  the  street  shall  be  provided  in  accordance  with  Sect.  101. 

1  The  importance  of  securing  high  quality  and  great  uniformity  in  the  surface 
course  cannot  be  urged  too  strongly. 

2  This  requirement  must  be  strictly  enforced.     Otherwise  there  will  be  danger 
that  the  two  courses  may  not  properly  adhere  to  each  other.     It  is  the  writer's 
experience  that  if  this  rule  is  observed  there  will  be  no  danger  of  the  two  courses 
separating. 

3  The  purpose  of  this  rolling  is  mainly  to  evenly  compress  the  mass  and  thus 
secure  its  uniform  density.     It  also  produces  a  truer  surface  than  can  usually 
be  secured  by  ramming  alone. 

4  Among  engineers  there  is  quite  a  wide  difference  of  opinion  as  to  the  proper 
spacing  of  expansion  joints,  and,  in  fact,  as  to  the  necessity  or  advisability  of 
providing  them  at  all.     It  has  been  suggested  that  it  might  be  better  to  omit 


HYDRAULIC  CONCRETE  ROADWAY  PAVEMENT      77 

Expansion  joints  shall  also  be  provided  and  constructed  as  follows: 
Wherever  the  width  of  the  pavement  exceeds  twenty  (20)  feet  between 
curbs  there  shall  be  a  expansion  joint  along  the  longitudinal  center 
of  the  street;  expansion  joints  shall  also  be  made,  at  right  angles  to 
the  street  and  extending  continuously  from  curb  to  curb,  at  distances 
apart  not  exceeding  twenty  (20)  feet.  These  expansion  joints  in  the 
body  of  the  pavement  shall  be  made  by  cutting  entirely  through  both 
courses  of  concrete  along  a  straight  line,  using  a  special  straight- 
edged  cutter  not  more  than  three-sixteenths  (3/16)  inch  thick,  when 
the  concrete  is  laid  in  hot  weather  and  not  more  than  three-eighths 
(3/8)  inch  thick  if  the  concrete  is  laid  when  the  thermometer  is  below 
sixty  (60)  degrees  F.  The  cutting  of  the  expansion  joints  shall  be 
carefully  and  skillfully  done,  and  after  each  joint  is  cut  a  special  T- 
shaped  smoother,  the  stem  of  which  is  one  inch  deep  and  of  the  same 
thickness  as  the  cutter  shall  be  worked  back  and  forth  in  the  joint 
until  the  edge  of  the  concrete  adjoining  the  joint  shall  be  well  and 
smoothly  compacted.  The  smoother  shall  be  so  formed  as  to  round 
off  the  corners  of  the  concrete  to  a  circular  form  having  a  radius  of 
one- fourth  (1/4)  inch.  All  these  operations  shall  be  completed 
before  the  concrete  has  begun  to  set.  After  the  concrete  has  set  and 
before  the  street  is  opened  to  travel  all  expansion  joints  shall  be 
poured  full  of  bituminous  cement,  as  specified  in  Section  go.1 

122.  Bituminous  Coating.2 — After  the  concrete  shall  have  become 
fully  set  as  determined  by  the  engineer  and  before  the  street  is 

them  entirely,  allowing  the  pavement  to  form  its  own  expansion  joints  by  cracking 
along  lines  where  natural  forces  dictate.  Such  cracks  by  their  irregularity  give 
a  bad  appearance  to  the  surface,  but  observation  seems  to  indicate  that  the  edges 
of  these  natural  joints  wear  as  well  a's  those  made  by  expansion  joints.  Further 
observation  and  experience  is  needed  in  the  matter.  In  most  concrete  it  is 
known  that  some  contraction  takes  place  during  the  setting  of  the  cement, 
regardless  of  temperature  changes,  and  cracking  is  probably  due  as  much  to 
this  permanent  contraction  as  to  that  caused  by  low  temperature.  The  coeffi- 
cient of  expansion  of  concrete  by  heat  is  variable  but  so  small  that  expansion 
joints  1/8  inch  wide  every  fifty  feet  along  the  street  should  provide  for 
temperature  changes. 

1  If  the  expansion  joints  are  not  thus  filled  with  bituminous  cement  they  will 
become  filled  and  packed  with  incompressible  stone,  sand,  etc.,   that  will  not 
permit  expansion. 

2  The  practical  value  of  oiling  concrete  pavements  has  not  yet  been  determined 
by  sufficient  experience.     There  is  reason,  however,  to  believe  that  the  slight 
coating  of  bitumen  will  materially  preserve  the  surface  from  abrasion  and  that 
its  benefit  will  thus  be  greater  than  its  cost.     It  will  also  tend  to  prevent  the  very 
slight  dust  that  might  otherwise  exist  on  the  pavement. 


78  STREET  ROADWA  Y  PA  VEMENTS 

opened  to  travel  the  whole  surface  of  the  pavement  shall  be  covered 
by  a  finishing  coat  of  bituminous  road  oil  as  hereinafter  specified. 

The  road  oil  shall  be  prepared  from  native  asphalt  or  from  a  crude 
oil  having  an  asphaltic  base.  Not  less  than  95  per  cent,  of  the  oil 
shall  be  soluble  in  cold  carbon  disulphide,  and  it  shall  contain  not 
less  than  thirty  (30)  per  cent,  of  solid  asphalt,  nor  more  than  ten  per 
cent,  of  fixed  carbon.  It  shall  be  of  such  consistency  as  to  flow  freely 
at  a  temperature  of  seventy-five  degrees  (75°)  F.  The  oil  shall  not 
be  applied  except  when  the  road  surface  is  perfectly  dry  and  when 
the  temperature  of  the  air  is  not  below  60°  F. 

The  oil  shall  be  evenly  distributed  over  the  whole  surface  of  the 
street  at  the  rate  of  one-half  (1/2)  gallon  of  oil  per  square  yard  of 
surface,  and  well  worked  over  the  surface  with  squeegees  or  other 
suitable  devices. 

Not  less  than  twenty-four  hours  after  the  application  of  the  oil 
the  surface  of  the  pavement  shall  be  evenly  covered  to  a  depth  of  one- 
fourth  inch  with  clean,  dry  stone  screenings  or  coarse  sand,  after 
which  the  street  may  be  opened  to  travel. 


GENERAL    SPECIFICATIONS   FOR   EXPERIMENTAL   OR 
UNTRIED  PAVEMENTS1 

123.  Contractors  or  promoters  submitting  proposals  for  the  con- 
struction of  new,  experimental,  or  special  street  pavements,  the 
merits  of  which  have  not  been  established  by  experience  in  the  city 

of ,  must  submit  with  their 

proposal  a  full  and  complete  set  of  specifications  for  the  construction 
of  the  pavement.     If  contract  shall  be  awarded  under  said  proposal, 
said  specifications  will  be  made  a  part  of  the  contract  entered  into. 
The  Engineer  will  enforce  compliance  with  these  specifications,  as 
the  construction  work  proceeds,  without  assuming  or  incurring  any 
responsibility  for  the  character,  quality,  serviceability  or  durability 
of  the  resulting  pavement.     But  the  Contractor  shall  be  subject 
to  and  shall  comply  with  the  requirements  and  stipulations  of  Sects, 
i  to  25,  inclusive,  of  these  specifications. 

124.  Special  Guaranty.2 — Inasmuch  as  the  pavement  to  be  con- 

1  In  this  class  of   pavements  the  contractor  or  promoter  may  properly  be 
required  to  assume  responsibility  for  the  character  and  utility  of  the  work  pro- 
duced, and  the  municipal  authorities  should  assume  no  part  of  such  responsibility. 

2  Upon  the  general  subject  of  time  guarantees  of  municipal  work,  see  Chapter 
XI,  "Municipal  Public  Works,"  by  the  author. 


EXPERIMENTAL  PA  VEMENTS  79 

structed  under  the  special  specifications  submitted  by  the  Contractor 
is  more  or  less  of  an  experimental  character,  having  not  been  here- 
tofore used  in  the  city  of  to  an  extent 

sufficient  to  establish  its  value,  the  Contractor  shall  be  held  wholly 
responsible  for  the  utility,  serviceability  and  durability  of  the  pave- 
ment so  constructed;  and  he  shall  enter  into  a  guaranty  to  the  effect 
as  follows: 

That  the  pavement  will  fulfill  all  the  usual  and  legitimate  re- 
quirements of  a  satisfactory  roadway  pavement  upon  the  street 
upon  which  it  is  to  be  laid. 

That  the  pavement  will  successfully  serve  and  endure  the  travel 

to  which  the  street  may  be  subjected  for  a  period  of 

years  next  following  the  date  of  the  certificate  of  its  completion  and 
acceptance,  and  shall  be  in  good  condition  at  the  end  of  that  period, 
ordinary  and  reasonable  wear  and  tear,  and  accidental  or  other  in- 
juries not  due  to  defects  in  the  pavement  itself,  excepted. 

That  the  Contractor  will,  at  his  own  cost,  keep  the  said  pave- 
ment in  satisfactory  repair  during  said  period  of 

years,  and  will  leave  it  in  a  condition  of  satisfactory  repair  at  the 
end  of  that  period. 

That  the  Engineer,  or  his  successor  or  successors  in  office,  shall 
be  the  sole  and  final  judge  as  to  whether  the  conditions  of  this  guar- 
anty shall  be,  or  shall  have  been  complied  with. 

That  in  case  the  pavement  shall  not,  in  the  judgment  of  the 
Engineer,  fulfill  the  terms  and  conditions  of  this  guaranty  at  any 

time  during  said  period  of years,  or  upon 

its  expiration;  or  in  case  the  Contractor  shall  fail  to  make  all  or  any 
of  the  repairs  that  may  in  the  judgment  of  the  Engineer  be  or  be- 
come necessary  during  said  period  of years, 

within  a  reasonable  period  to  be  determined  by  the  Engineer,  but 
not  to  be  less  than  twenty  (20)  days  after  notice  to  make  such 
repairs  has  been  given  him  by  the  Engineer,  he  (the  Engineer)  may 
proceed  to  make  or  to  have  made  such  repairs,  or  to  repave  the 
street,  in  any  manner  that  he  may  deem  necessary  or  advisable,  and 
to  charge  the  cost  of  such  repairs  or  repavement  to  the  Contractor, 
provided,  that  the  sum  or  sums  so  charged  against  the  Contractor 
shall  not,  in  the  aggregate,  be  more  than  the  amount  paid  to  the 
Contractor  for  the  construction  of  the  pavement. 

125.  Bond. — The  Contractor  shall  give  bond  with  sureties  satis- 
factory to  the  Engineer  in  a  sum  not  less  than  the  estimated  cost  of 
the  pavement  at  the  contract  prices,  the  term  of  the  bond  to  extend 


80  STREET  ROA  DWA  Y  PA  VEMENTS 

over  the  entire  period  of years,  for  which  the 

pavement  is  guaranteed. 

126.  During    the    said    period    of years    the 

Contractor  shall,  upon  being  notified  by  the  Engineer  so  to  do,  make 
any  repairs  to  the  pavement  that  may  become  necessary  by  reason 
of  cutting  into  it  for  the  purpose  of  constructing  or  repairing  pipes, 
conduits  or  other  underground  structures,  or  street  railroad  tracks, 
or  by  reason  of  accidental  or  unusual  causes,  or  of  any  causes  other 
than  those  due,  in  the  opinion  of  the  Engineer,  to  the  failure  of  the 
pavement  to  meet  and  fulfill  the  terms  of  the  guaranty  stipulated 
in  Section  124.  And  for  making  such  repairs  the  Contractor  shall 

be  paid  the  price  of per  square  yard  for 

the  repairs  actually  so  made.  Repairs  so  made  shall  be  subject  to 
the  terms  of  the  guaranty,  stipulated  in  Section  124,  until  the  expi- 
ration of  the  said  term  of years  after  the  date 

of  the  original  certificate  of  completion  and  acceptance.  In  case 
the  Contractor  shall  neglect  or  fail  to  make  such  repairs  within  a 
period  of  twenty  (20)  days  after  he  shall  have  received  notice  to  do 
so,  the  Engineer  may  proceed  to  make  or  to  have  made  such  repairs, 
and  he  shall  charge  to  and  collect  from  the  Contractor  the  cost  of 
the  repairs  so  made. 


HYDRAULIC  CONCRETE  COMBINED  CURB  AND  GUTTER1 

127.  Hydraulic  concrete  combined  curb  and  gutter  shall  be  con- 
structed in  accordance  with  general  plan  No attached  to 

and  made  a  part  of  these  specifications,  but  the  rise  from  the  gutter 
to  the  top  of  the  curb  may  be  varied  so  as  to  facilitate  drainage.2 

1  Concrete  combined  curb  and  gutter  is  suitable  for  use  on  the  great  majority 
of  residence  streets,  and  others  where  the  travel  is  not  excessive,  or  where  it 
will  not  be  subjected  to  specially  severe  use,  as  on  business  streets  where  heavy 
vehicles  are  likely  to  be  often  backed  against  the  curb.     If  properly  constructed 
it  will  have  sufficient  hardness  and  strength  to  withstand  all  ordinary  usage;  it 
makes  a  better  appearance,  particularly  on  residence  streets,  than  any  other 
kind  of  curbing,  is  durable,  and  is  usually  less  expensive  than  any  other  suitable, 
equally  durable  and  equally  well-finished  curbing  of  natural  stone,  since  the 
gutter  displaces  an  equal  area  of  pavement. 

2  The  sketch  here  presented  conforms  pretty  closely  to  usual  practice  except 
in  the  width  of  the  gutter.     It  is  not  uncommon  to  make  the  gutter  from  two 
to  three  feet  wide.     This  is  not  necessary  or  desirable.     A  width  of  15  to  18 


HYDRAULIC  CONCRETE  CURB  AND  GUTTER  81 

128.  Excavation. — All  excavation  required  for  the  curb  and  gutter 
shall  be  completed  and  trimmed  to  the  proper  lines  as  shown  by  the 
drawing.     The  drainage  trench  under  the  curb  and  gutter  shown  on 
the  drawing  shall  have  the  top  width  and  general  form  shown  in  the 
drawing  but  its  depth  may  be  varied  to  secure  proper  drainage,  as 
the  engineer  may  direct,  provided  that  its  depth  below  the  base  of 
the  concrete  shall  not  be  less  than  nine  inches  nor  more  than  two 
feet. 

129.  Broken  Stone  Drainage.1 — After  the  excavation  shall  have 
been  completed  the  trench  shall  be  rilled  up  to  the  level  of  the  base 
of  the  concrete  with  sound,  durable  broken  stone,  or  coarse  gravel, 
from  which  the  small  fragments  shall  have  been  removed  by  screen- 
ing over  a  wire  screen  having  openings  not  less  than  one  inch  square. 
The  stone  or  gravel  shall  be  thoroughly  tamped  in  the  trench  in 
layers  not  more  than  six  (6)  inches  thick  by  the  use  of  rammers 
weighing  not  less  than  thirty  (30)  pounds  and  having  a  face  area 
not  exceeding  thirty-six  (36)  square  inches,  and  its  completed  top 
surface  shall  conform  truly  to  the  designed  base  of  the  concrete. 
These  drains  shall  be  connected  at  suitable  intervals  with  sewers, 
drains  or  other  outlets  to  keep  them  free  from  standing  water.     The 
trench  rilling  shall  be  completed  at  least  twenty-five  feet  in  advance 
of  placing  the  forms  for  the  concrete. 

130.  Concrete.2 — The  concrete  shall  be  made  of  one  (i)  part 

inches  forms  a  sufficient  gutter  to  carry  away  all  drainage  except  during  very 
heavy  rainfalls.     Where  the  gutter  nroiprte  ™if  ;-+-  -Ll- 


or  tne  rule  that  the  facing  course  must 
be  applied  before  the  core  concrete  has  begun  to  set.  But  it  is  difficult  to  always 
secure  these  favorable  conditions.  Computation  will  show  that  the  difference 
in  cost  of  materials,  between  the  usual  two-course  construction  and  a  single 
body  of  rich  concrete  throughout,  is  not  very  great,  while  the  saving  in  cost  of 
labor  is  so  considerable  as  to  make  the  actual  difference  in  cost  of  the  two  types 


80 


STREET  ROADWAY  PAVEMENTS 


over  the  entire  period  of years,  for  which  the 

pavement  is  guaranteed. 

126.  During    the    said    period    of years    the 

Contractor  shall,  upon  being  notified  by  the  Engineer  so  to  do,  make 
any  repairs  to  the  pavement  that  may  become  necessary  by  reason 
of  cutting  into  it  for  the  purpose  of  constructing  or  repairing  pipes, 
conduits  or  other  underground  structures,  or  street  railroad  tracks, 
or  by  reason  of  accidental  or  unusual  causes,  or  of  any  causes  other 
than  those  due,  in  the  opinion  of  the  Engineer,  to  the  failure  of  the 
pavement  to  meet  and  fulfill  the  terms  of  the  guaranty  stipulated 
in  Section  124.  And  for  making  such  repairs  the  Contractor  shall 

be  paid  the  price  of per  square  yard  for 

the  repairs  actually  so  made.  Repairs  so  made  shall  be  subject  to 
the  terms  of  the  guaranty,  stipulated  in  Section  124,  until  the  expi- 
ration of  the  said  term  of years  after  the  date 

of  the  original  certificate  of  completion  and  acceptance.  In  case 
the  Contractor  shall  neglect  or  fail  to  make  such  repairs  within  a 
period  of  twenty  (20)  days  after  he  shall  have  received  notice  to  do 
so,  the  Engineer  may  proceed  to  make  or  to  have  made  such  repairs, 
and  he  shall  charge  to  and  collect  from  the  Contractor  the  cost  of 
the  repairs  so  made. 


HYDRAULIC  CONCRETE  COMBINED  CURB  AND  GUTTER1 


^  Concrete  Combined      ff">         {' 
^    Curb  and  Gutter   »k 


gutter  displaces  an  equal  area  of  pavement. 

2  The  sketch  here  presented  conforms  pretty  closely  to  usual  practice  except 
in  the  width  of  the  gutter.  It  is  not  uncommon  to  make  the  gutter  from  two 
to  three  feet  wide.  This  is  not  necessary  or  desirable.  A  width  of  15  to  18 


HYDRAULIC  CONCRETE  CURB  AND  GUTTER  81 

128.  Excavation. — All  excavation  required  for  the  curb  and  gutter 
shall  be  completed  and  trimmed  to  the  proper  lines  as  shown  by  the 
drawing.     The  drainage  trench  under  the  curb  and  gutter  shown  on 
the  drawing  shall  have  the  top  width  and  general  form  shown  in  the 
drawing  but  its  depth  may  be  varied  to  secure  proper  drainage,  as 
the  engineer  may  direct,  provided  that  its  depth  below  the  base  of 
the  concrete  shall  not  be  less  than  nine  inches  nor  more  than  two 
feet. 

129.  Broken  Stone  Drainage.1 — After  the  excavation  shall  have 
been  completed  the  trench  shall  be  filled  up  to  the  level  of  the  base 
of  the  concrete  with  sound,  durable  broken  stone,  or  coarse  gravel, 
from  which  the  small  fragments  shall  have  been  removed  by  screen- 
ing over  a  wire  screen  having  openings  not  less  than  one  inch  square. 
The  stone  or  gravel  shall  be  thoroughly  tamped  in  the  trench  in 
layers  not  more  than  six  (6)  inches  thick  by  the  use  of  rammers 
weighing  not  less  than  thirty  (30)  pounds  and  having  a  face  area 
not  exceeding  thirty-six  (36)  square  inches,  and  its  completed  top 
surface  shall  conform  truly  to  the  designed  base  of  the  concrete. 
These  drains  shall  be  connected  at  suitable  intervals  with  sewers, 
drains  or  other  outlets  to  keep  them  free  from  standing  water.     The 
trench  filling  shall  be  completed  at  least  twenty-five  feet  in  advance 
of  placing  the  forms  for  the  concrete. 

130.  Concrete.2 — The  concrete  shall  be  made  of  one  (i)  part 

inches  forms  a  sufficient  gutter  to  carry  away  all  drainage  except  during  very 
heavy  rainfalls.  Where  the  gutter  projects  out  into  the  street  sufficiently  far 
to  be  exposed  to  large  numbers  of  heavily  loaded  wheels  the  outer  corner  is 
likely  to  become  broken  off  or  unduly  abraded. 

1  Curbing   of   all   kinds    is   more   likely   to   be  injured  by  freezing  and  the 
heaving  of  frost  under  and  around  it  than  from  any  other  cause.     Good  drainage 
is  the  best  protection  against  such  injury.     It  is  important  that  these  drains 
shall  be  connected  with  sewers,  drains  or  other  outlets,  so  that  water  will  not 
stand  in  them. 

2  The  most  notable  departure  of  these  specifications  from  usual  practice  is 
the  use  of  a  solid  body  of  rich,  homogeneous  concrete  for  the  whole  section  of  the 
structure,  thus  avoiding  the  use  of  two  courses  and  qualities  of  concrete — the 
core  concrete  and  the  facing.     The  most  common  cause  of  failure  of  concrete 
curbs  and  gutters  is  the  separation,  more  or  less,  of  the  facing  from  the  core 
concrete.     Without  doubt  this  can  be  prevented  by  the  use  of  proper  materials, 
careful  work,  and  the  strict  observance  of  the  rule  that  the  facing  course  must 
be  applied  before  the  core  concrete  has  begun  to  set.     But  it  is  difficult  to  always 
secure  these  favorable  conditions.     Computation  will  show  that  the  difference 
in  cost  of  materials,  between  the  usual  two-course  construction  and  a  single 
body  of  rich  concrete  throughout,  is  not  very  great,  while  the  saving  in  cost  of 
labor  is  so  considerable  as  to  make  the  actual  difference  in  cost  of  the  two  types 


82  STREET  ROADWA  Y  PA  VEMENTS 

Portland  cement,  one  and  three-fourths  (i  3/4)  parts  of  sand  and 
three  (3)  parts  of  crushed  stone  or  clean  gravel.  The  Portland 
cement  shall  comply  in  all  respects  with  the  requirements  of  Section 
29  of  these  specifications. 

The  sand  shall  be  clean,  sharp  silicious  sand  made  up  of  grains 
of  such  size  that  not  more  than  fifteen  per  cent.  (15%)  will  pass  a 
number  thirty  (30)  sieve.  It  shall  not  contain  more  than  five  per 
cent.  (5%)  of  clay  or  loam  nor  more  than  two  per  cent.  (2%)  of 
organic  matter  or  other  refuse.  The  stone  shall  be  sound,  hard, 
durable,  and  freshly  broken,  free  from  clay,  loam,  organic  matter, 
or  other  impurities.  Trap  rock  or  granite  will  be  preferred,  but 
limestone,  if  hard  and  sound,  may  be  used  with  the  approval  of  the 
engineer.  Only  those  fragments  of  the  crushed  stone  that  pass  a 
screen  with  openings  three-fourths  inch  square  and  those  that  are 
held  on  a  screen  with  openings  one-fourth  inch  square  shall  be  used 
in  the  concrete. 

131.  Mixing  and  Placing  Concrete. — The  concrete  shall  be  mixed 
in  accordance  with  Section  35  of  these  specifications.     Very  thorough 
mixing  will  be  required. 

The  mixed  concrete  shall  be  handled  so  as  to  prevent  as  far  as 
practicable  any  separation  or  segregation  of  the  stone  and  mortar. 
When  in  place  it  shall  be  compacted  by  tamping  and  where  placed 
against  forms,  forking  or  other  effective  means  must  be  used  to 
bring  mortar  to  the  surface  and  to  secure  complete  contact  between 
mortar  and  forms,  so  as  to  leave  a  solid,  homogeneous  and  unbroken 
surface  when  the  forms  are  removed.  Where  the  concrete  may  not 
be  laid  against  forms,  all  exposed  surfaces  must  be  troweled  to  a 
true  surface  conforming  accurately  to  the  lines  shown  by  the  plans, 
templates  and  straight-edges  being  used  where  necessary. 

132.  Weather. — Concrete   in   combined   curb   and  gutter  shall 
not  be  laid  in  freezing  weather  nor  shall  frozen  materials  be  used 
in  the  work.     Completed  work  must  be  securely  protected  from 
frost  for  at  least  seven  days  after  it  is  laid.     Any  concrete  curb 
and  gutter  that  may  become  frozen  within  that  period  shall  be  wholly 
removed  and  replaced  with  new  work. 

133.  Expansion  Joints. — The  combined  curb  and  gutter  shall  be 
divided  into  blocks  or  panels  not  more  than  twelve  feet  long,  by 
clear,  open  expansion  joints  perpendicular  to  the  face  of  the  curb, 

very  small.  There  can  be  no  doubt  that  the  simpler  construction  and  the  con- 
sequent greater  certainty  of  securing  a  durable  and  satisfactory  job  is  greatly 
in  favor  of  the  construction  here  recommended. 


HYDRAULIC  CONCRETE  CURB  AND  GUTTER        83 

extending  entirely  and  continuously  through  the  whole  mass  of 
the  concrete.  These  expansion  joints  shall  be  three-eighths  inches 
wide  and  may  be  formed  either  by  cutting  through  the  completed 
curb  and  gutter  with  a  suitable  tool,  or  by  the  use  of  iron  forms 
or  partitions,  but  in  either  case  the  corners  at  the  ends  of  the 
blocks  must  be  made  solid  and  dense  and  troweled  with  a  suitable 
tool. 

134.  Circular  Corners. — At  the  intersections  of  streets,  circular 
corners,  having  a  radius  equal,  generally,  to  one-fifth  of  the  width 
of  the  roadway  of  the  narrower  street,  shall  be  constructed  of  the 
same  dimensions  and  quality  as  on  the  body  of  the  street,  and  the 
curb  and  gutter  will  be  extended  along  the  line  of  the  cross  street 
back  to  the  front  lot-lines.  Properly  curved  circular  curb  and  gutter 
shall  also  be  constructed  at  all  angles  exceeding  five  degrees  in  the 
line  of  the  curbing. 

J35'  Corner  Protection. — Galvanized  steel  corner  protectors  or 
nose-pieces  shall  be  used  to  protect  the  upper  and  outer  corner  of  the 
curb  at  all  circular  corners  and  angles  in  the  street.  This  steel 
protection  may  be  of  any  pattern  or  section  procurable  in  the  market 
and  approved  by  the  engineer.  It  shall  be  firmly  anchored  and  se- 
cured into  the  concrete. 

136.  Finishing. — After  the  forms  have  been  removed  and  before 
the  concrete  has  set  up  too  hard  to  be  affected  by  the  brush,  the  face 
and  top  of  the  curb  shall  be  lightly  scrubbed  by  a  suitable  wire 
brush  so  as  to  completely  remove  any  glazed  surface  and  to  produce 
a  surface  of  uniform  texture  and  appearance.     Dry  cement  or  neat 
cement  mortar  shall  not  be  used  for  dressing  up  exposed  surfaces.1 

137.  Forms. — The  forms  used  may  be  of  dressed  lumber  or  of 
metal  as  the  contractor  may  prefer.     But  they  shall  have  sufficient 
strength  and  rigidity  to  hold  the  concrete  firmly  in  place,  and  to  pre- 
serve the  correct  dimensions,  alignment  and  levels  of  the  curb  and 
gutter. 

.138.  Protection. — The  completed  curb  and  gutter  shall  be  pro- 
tected from  fracture,  deformation  or  spalling  until  the  concrete  has 
fully  set.  The  concrete  must  be  kept  moist  for  at  least  five  days 

1  The  appearance  of  "hair  cracks"  on  the  surface  of  rich  concrete,  finished  by 
troweling,  and  the  blotched  appearance  of  the  surface  of  concrete  curbing,  are 
usually  caused  by  improper  finishing.  The  glazed  surface  produced  by  trowel- 
ing, particularly  where  pure,  dry  cement  or  neat  mortar  is  applied  is  almost 
sure  to  develop  hair  cracks,  and  the  varying  texture  of  the  surface  is  likely  to 
absorb  water  unevenly  and  thus  produce,  in  time,  the  unevenly  colored  or 
blotched  surface  so  often  seen. 


84  STREET  ROA  DWA  Y  PA  VEMENTS 

after  it  has  been  laid.  Any  part  of  the  curb  and  gutter  that  shall 
have  become  injured  before  it  is  accepted  or  the  street  is  opened  for 
travel  shall  be  taken  up  and  replaced  by  the  contractor. 

139.  Payment. — Concrete  combined  curb  and  gutter  will  be  paid 
for  by  the  linear  foot  in  place,  the  measurement  to  be  made  along 
the  upper  and  outer  corner  of  the  curb.  The  price  per  linear  foot 
named  in  the  contract  will  cover  all  the  excavation  or  grading  re- 
quired and  all  the  materials  and  labor,  including  all  necessary 
forms,  for  constructing  the  curb  and  gutter  complete.  But  the 
crushed  stone  used  for  drainage  will  be  paid  for  by  the  cubic  yard 
measured  in  place,  and  steel  corner  protection  will  be  paid  for  by 
the  linear  foot  in  place,  at  the  prices  named  in  the  contract. 


HYDRAULIC  CONCRETE  SIDEWALKS 

Note. — These  specifications  conform  to  the  common  practice  of  laying 
the  sidewalk  in  two  courses. 

In  the  author's  judgment  this  is  neither  necessary  nor  desirable.  He 
believes  that  it  would  be  better  and  somewhat  cheaper  to  use  a  single 
course  of  concrete  four  inches  in  thickness.  He  suggests  for  this  concrete 
the  ratios  of  one  cement,  two  sand,  and  three  and  one-half  stone,  the  latter 
to  be  crushed  to  pass  a  screen  with  five-eighths  inch  square  openings. 

Tamping  will  bring  a  sufficient  quantity  of  mortar  to  the  surface  to 
permit  of  satisfactory  finishing.  While  the  materials  for  such  a  single 
course  of  four  inch  concrete  would  cost  somewhat  more,  the  saving  in 
cost  of  labor  would,  at  usual  prices  of  material  and  labor,  make  the  single- 
course  construction  somewhat  cheaper,  while  the  solid  four  inches  of 
richer  concrete  would  make  the  walk  much  stronger.  In  fact,  a  single 
course  of  such  concrete  three  inches  thick  would  be  sufficient  in  a  great 
majority  of  cases.  While  the  surface  might  not  have  the  glazed  appear- 
ance common  in  the  two-course  work  it  would  be  really  better  for  use — a 
polished  and  slippery  surface  on  sidewalks  is  not  desirable. 

SPECIFICATIONS  l 

140.  The  hydraulic  concrete  sidewalk  shall  be 

feet  in  width  and  its  outer  edge  shall  be feet  from 

1  "The  utility  and  durability  of  hydraulic  concrete  sidewalks  depends  largely 
on  the  quality  of  materials  and  workmanship  employed  in  the  work.  Too 
frequently,  specifications  for  this  work  are  not  sufficiently  full,  or  not  prepared 
with  the  requisite  care,  or  the  work  is  not  properly  supervised  or  inspected 
while  in  progress.  The  aggregate  importance  and  cost  of  this  sidewalk  work 
in  our  cities  warrants  more  care  and  attention  than  it  generally  receives. 


HYDRAULIC  CONCRETE  SIDEWALKS  85 

the  outer  face  of  the  street  curbing.     It  shall  be  constructed  with 
two  courses  of  Portland  cement  concrete  as  hereinafter  specified. 

141.  Excavation  and  Grading. — The  ground  to  be  occupied  by  the 
sidewalk  shall  be  excavated  or  filled  to  a  sub-grade  which  after  being 

compacted  shall  be inches1  below  the  finished 

surface  of  the  sidewalk.     The  sub-grade  shall  be  neatly  dressed  to  a 
plane  surface  sloping  downward  toward  the  street  one-fourth  inch  in 
one  foot  horizontal,  and  to  such  longitudinal  gradients  as  the  engi- 
neer may  prescribe.     The  completed  sub-grade  shall  project  four  (4) 
inches  in  excavation  and  eighteen  (18)  inches  in  "embankment  on 
each  side  beyond  the  edges  of  the  completed  sidewalk.     After  the 
grading  is  completed  the  surface  shall  be  compacted  by  rolling  or 
ramming. 

142.  Drainage  Course. — Upon  the  sub-grade  prepared  as  speci- 
fied in  Section  141  a  drainage  course  composed  of  broken  stone, 

gravel  or  boiler-plant  cinders, inches2  in  thickness 

shall  be  laid.     Broken  stone  for  this  purpose  may  be  of  any  durable 
stone  crushed  to  such  size  that  all  will  pass  through  a  screen  with  two 
inch  openings.     Crusher-run  material  may  be  used  unless  it  contains 
an  excessive  quantity  of  fine  material.     Gravel  for  the  purpose  may 
be  any  sound  durable  gravel  all  of  which  will  pass  through  a  two  inch 
screen  and  be  retained  upon  a  one-fourth  (1/4)  inch  screen.     If 
cinders  are  used  they  must  be  good  boiler-plant  cinders  from  which 
the  ashes  have  been  screened  out.     The  cinders  must  be  thoroughly 
drenched  with  water  at  least  one  week  before  they  are  placed  in  the 
sidewalk.3 

1  Determined  by  the  thickness  of  the  drainage  course  adopted. 

2  It  is  customary  in  many  cities  to  require  that  the  drainage  course  under  the 
concrete  shall  have  a  depth  of  twelve  or  more  inches.     This  deep-drainage  is 
designed  to  prevent  the  heaving  of  the  sidewalk  by  freezing.     Experience  seems 
to  prove  that  this  is  not  necessary,  particularly  if  tile  drains  are  provided  to  carry 
off  the  water  from  the  drainage  course,  as  specified.     Comparatively  dry  material, 
even  earth,  does  not  heave  with  freezing;  on  the  other  hand,  if  the  material  and 
the  trench  in  which  it  is  placed  is  wholly  or  partly  filled  with  water,  heaving  is 
liable  to  occur  in  severe  freezing  weather,  whatever  the  depth  of  the  drainage 
course.     Experience  has  proven,  however,  that  four  inches  of  drainage  material 
is  sufficient  if  the  water  is  drained  out  of  it,  while  if  allowed  to  stand  saturated 
with  water,  deeper  drainage  will  give  little  if  any  better  results.     Where  the  soil 
is  sandy  or  the  natural  drainage  is  otherwise  good,  no  drainage  course  is  necessary. 

3  Except  in  the  matter  of  low  first  cost  cinders  are  not  desirable  for  the  drainage 
course.     In  time,  this  material  is  likely  to  slack,  or  decompose,  and  shrink  in 
volume  more  or  less  and  to  allow  the  sidewalk  to  settle.     The  hollow  sound  one 
often  notices  when  walking  over  a  sidewalk  and  the  cracks  tha  t  frequently  appear, 


86  STREET  ROA  DWA  Y  PA  VEMENTS 

143.  This  drainage  material  shall  be  placed  on  the  sub-grade  and 
properly  graded.     After  grading  it  shall  be  thoroughly  compacted 
by  ramming  or  rolling,  and  its  surface  shall  be  brought  to  a  plane 

parallel  to  and inches  below  the  designed  surface 

of  the  sidewalk,  after  which  the  surface  inequalities  may  be  leveled 
up  with  screenings  or  small  gravel. 

The  bottom  of  the  drainage  course  shall  be  connected  with  the 
street  drains  or  sewer  inlets  by  three-inch  hard  drain  pipe  at  such 
points,  not  nore  than  three  hundred  feet  apart,  as  will  drain  all 
standing  water  out  of  the  drainage  course. 

144.  Concrete,  Bottom  Course. — The  bottom  course  of  concrete 

L  inches  in  depth,  shall  be  constructed  and  placed 

in  accordance  with  Sections,  28,  29,  30,  31,  32,  33,  34,  35  and  36 
of  these  general  specifications,  except  that  the  maximum  size  of 
the  crushed  stone  shall  not  exceed  one-half  the  thickness  of  the  bot- 
tom course  of  concrete  and  the  concrete  shall  be  uniformly  composed 
of  one  part  Portland  cement,  three  parts  sand  and  six  parts  of 
crushed  stone.     Its  upper  surface  shall  be  brought  to  a  plane  parallel 
to  and  one  inch  below  the  designed  sidewalk  surface. 

145.  Surface  or  Finishing  Course. — The  surface  or  finishing  course 
shall  be  of  concrete,  one  inch  thick,  composed  of  one  part  Portland 
cement,  one  and  one-half  parts  sand  and  two  and  one-half  parts  of 
hard,  durable  stone,  crushed  to  such  sizes  that  all  will  pass  through 
a  screen  having  openings  one-half  (1/2)  inch  square  and  none  will 
pass  through  a  screen  having  openings  one-eighth  (1/8)  inch  square.2 
This  concrete  shall  be  made  a?  specified  in  Sections  28,  29,  30, 31,32, 
33>  34>  35  and  36  except  in  the  particulars  named  in  the  preceding 
paragraph.     Care  must  be  taken  to  make  the  mixing  very  thorough. 
The  quantity  of  water  used  in  this  concrete  shall  be  just  suffi- 
cient to  make  a  moderately  wet  mixture,  and  care  shall  be  taken 

are  usually  caused  by  the  irregular  settlement  of  the  drainage  course.  The  object 
of  wetting  down  the  cinders  several  days  before  they  are  used  is  to  cause  as  much 
as  possible  of  this  slacking  to  take  place  before  the  cinders  are  used  in  the 
drainage  course. 

1  There  is  a  good  deal  of  diversity  of  practice  in  the  thickness  of  the  concrete 
to  be  used.  For  all  ordinary  sidewalks  three  inches  of  bottom  course  and  one 
inch  of  surface  course  are  ample,  and  in  many  cases  the  thickness  of  the  surface 
course  has  been  reduced  to  one-half  inch  with  satisfactory  results.  Three- 
fourths  inch  of  surface  course,  if  fairly  uniform  in  thickness  and  of  good  quality, 
will  generally  be  ample  for  ordinary  sidewalks. 

2  It  is  customary  to  make  the  surface-course  concrete  much  richer  than  this, 
but  it  is  not  necessary  if  the  materials  are  good  and  the  work  well  done. 


HYDRAULIC  CONCRETE  SIDEWALKS  87 

to  make  the  different  batches  as  nearly  as  practicable  of  the  same 
consistency. 

The  surface  concrete  shall  be  spread  over  the  bottom-course  con- 
crete before  the  latter  has  begun  to  set,1  properly  graded,  well  com- 
pacted by  ramming,  and  its  upper  surface  brought  to  the  true  de- 
signed plane  and  surface  of  the  sidewalk  by  the  use  of  straight  edges 
and  troweling,2  after  which  the  surface  shall  be  lightly  gone  over 
with  a  wire  broom  or  brush  to  slightly  roughen  the  surface.  The 
finished  plane  of  the  sidewalk  shall  have  a  transverse  downward 
slope  toward  the  street  of  one-fourth  (1/4)  inch  to  one  foot  of  hori- 
zontal width.  At  no  place  shall  the  thickness  of  the  surface  course 
be  less  than  three-fourths  of  one  inch.  The  outer  top  corners  of  the 
sidewalk  shall  be  rounded  off  with  a  suitable  tool  to  a  radius  of  three- 
fourths  (3/4)  inch. 

146.  Forms. — Substantial  and  suitable  forms  of  wood  or  iron 
shall  be  furnished  and  used  by  the    contractor   to  support  the 
concrete  until  it  is  hard  set,  when  they  shall  be  removed  at  his 
expense. 

147.  Expansion  Joints. — After  the  laying  of  both  courses  of  con- 
crete is  completed  expansion  joints  at  right  angles  to  the  sidewalk, 
and  not  more  than  four  (4)  feet  apart  shall  be  constructed  in  the  side- 
walk in  the  following  manner:  the  joint  will  be  located  by  a  line  on 
the  surface  of  the  sidewalk  and  a  straight- edged  cutting  tool  one- 
fourth  (1/4)  inch  thick  will  be  used  to  cut  entirely  through  both 
courses  of  concrete,  accurately  along  the  line  marked  out,  entirely 
across  the  sidewalk,  after  which  a  T-shaped  trowel  or  tool  shall  be 
used  to  smooth  and  compact  the  cut  surfaces  for  a  depth  of  one 
inch,  and  to  round  off  the  corners  of  the  sidewalk  blocks  to  a  radius 
of  one-fourth  (1/4)  inch.3 

Where  the  ends  of  the  sidewalk  abut  against  the  curbing  a  clear 

1  This  requirement  is  very  important  and  should  be  strictly  enforced,  other- 
wise there  is  danger  that  by  the  action  of  water,  frost,  and  time,  the  two  courses 
may  separate  and  the  surface  course  break  up — a  condition  not   infrequently 
observed. 

2  The  troweling  not  only  helps  to  secure  a  true  surface,  but  tends  to  produce  a 
dense  surface  on  the  concrete;  but  it  is  not  desirable  that  this  surface  shall  be 
smooth  and  glassy,  hence  the  slight  roughening  of  the  surface  with  a  wire  brush. 

3  Care  must  be  taken  to  make  and  leave  these  expansion  joints  open  to  their 
full  width  entirely  through  the  concrete.     The  practice  of  forming  these  expan- 
sion joints  by  partitions  of  iron  plate,  against  which  the  blocks  of  sidewalk  are 
built  is  not  advised,  for  the  reason  that  they  are  likely  to  prevent  the  thorough 
compression  of  the  concrete  surface  against  or  near  the  plates. 


88  STREET  ROA  DWA  Y  PA  VEMENTS 

expansion  joint  one  and  one-fourth  (i  1/4)  inches  wide  shall  be 
left  between  the  sidewalk  and  the  curb. 

148.  After  the  concrete  laying  is  completed  it  shall  be  protected 
from  use  or  injury  until  the  concrete  is  set  hard  enough  to  withstand 
travel,  and  it  shall  be  kept  continuously  damp  for  at  least  five  days 
after  the  concrete  is  laid. 

149.  Weather. — Concrete  in  sidewalks  shall  not  be  laid  in  freezing 
weather  nor  shall  frozen  materials  be  used  in  the  work.     Completed 
work  must  be  securely  protected  from  frost  -for  at  least  seven  days 
after  the  concrete  is  laid.     Any  concrete  sidewalk  that  shall  become 
frozen  within  that  period  of  time  shall  be  wholly  taken  up  and 
replaced  with  new  work,  at  the  expense  of  the  contractor. 

150.  Regrading. — Directly    after    the    concrete    is    completed, 
the  forms  removed,  and  the  work  inspected  by  the  engineer,  the 
space  between  the  outer  edge  of  the  sidewalk  and  the  street  curb 
shall  be  excavated  or  filled  up  and  dressed  to  a  plane  one  inch 
below  the  top  of  the  sidewalk  and  the  top  of  the  street  curb;  and  the 
space  on  the  inner  side  of  the  sidewalk  shall  be  graded  to  a  plane 
one  inch  below  and  parallel  to  the  surface  of  the  sidewalk  for  a 
distance  of  two  feet  back  from  the  edge  of  the  sidewalk  and  com- 
pleted with  a  slope  of  one  and  one-half  to  one  to  the  natural  surface 
of  the  ground.     Where  this  regrading  requires  filling  up  the  filling 
material,  for  a  depth  of  four  inches  from  the  surface,  shall  be  good, 
rich  surface*  soil. 

151.  Should  any  defects  due  to  faulty  material  or  workmanship 
develop  in  the  sidewalk  within  one  year  after  the  completion  of 
the  same  the  contractor  shall  repair  or  reconstruct  all  such  defective 
places  at  his  expense,  doing  the  work  in  accordance  with  these 
specifications. 

152.  Measurement  and  Payment. — Concrete  sidewalk  will  be 
measured  and  paid  for  by  the  square  foot  of  completed  sidewalk 
surface,  and  the  unit  price  per  square  foot  shall  cover  the  entire 
cost  of  the  work,  including  grading,  drainage  work,  all  material 
and  labor,  forms,  and  the  regrading  or  dressing  up  after  the  comple- 
tion of  the  concrete  work;  except  that  the  drain  pipe  used  will  be 
paid  for  per  linear  foot  at  the  price  named  in  the  contract  which 
price  shall  cover  the  cost  of  furnishing  and  putting  the  pipe  in 
place  complete. 


PART  II 

INSTRUCTIONS  TO  INSPECTORS  ON  STREET 
PAVING  WORK 


INTRODUCTORY  NOTE 

Any  general  code  of  instructions  for  inspectors  on  street  paving 
work  must  necessarily  be  little  more  than  tentative  or  suggestive,  as 
applied  to  any  one  city. 

That  here  presented  is  intended  for  use  in  connection  with  the 
specifications  in  Part  I  of  this  book.  Different  specifications  might 
make  necessary  many  changes  in  the  instructions  that  follow.  The 
local  or  special  conditions  in  any  city  might  also  make  them  in- 
applicable without  material  modifications  and  additions. 

The  author  believes  that  in  every  city  where  considerable  street 
pavement  work  is  prosecuted  and  a  number  of  inspectors  employed 
on  such  work,  some  such  code  of  instruction?  to  inspectors  should  be 
formulated  and  used.  Even  where  the  inspectors  are  of  high  char- 
acter and  fully  competent,  the  adoption  of  a  system  of  rules  and  reg- 
ulations relating  to  their  work  will. tend  to  unify  procedure,  prevent 
misunderstandings  and  promote  good  discipline. 

The  preparation  of  such  a  code  of  instructions  requires  no  little 
time  and  thought,  especially  where  there  are  no  precedents  to  sug- 
gest what  is  needed,  or  to  be  used  as  rough  patterns.  It  is  with  the 
hope  that  the  code  here  presented  may  be  found  useful  in  this  way, 
even  though  it  may  be  not  appropriate  for  adoption  in  any  given 
city,  that  it  is  offered  to  municipal  engineers. 

GENERAL  REMARKS  ABOUT  INSPECTION  AND  INSPECTORS 

The  necessity  of  having  competent  and  honest  inspectors  upon 
any  public  work  during  its  construction  need  not  be  here  argued.  It 
is  generally  understood  and  recongized  in  the  case  of  work  carried 
out  by  contract.  Where  the  contractor  is  incompetent,  careless  or 
unreliable,  inspection  is  absolutely  necessary  if  good  work  is  to  be 
secured.  Even  where  the  contractor  thoroughly  understands  his 
business  and  intends  to  faithfully  comply  with  the  specifications  and 
to  do  all  his  work  in  a  proper  manner,  the  inspector  cannot  safely 
be  dispensed  with.  The  contractor  cannot  at  all  times  be  on 
the  work;  whatever  may  be  his  intention  and  instructions,  fore- 
men and  laborers -cannot  be  depended  upon  to  exercise  the  proper 

91 


92  STREET  ROADWA  Y  PA  VEMENTS 

care  and  judgment,  even  where  they  have  no  inclination,  motive 
or  interest  to  do  otherwise,  which  is  not  always  the  case.  It  seems 
to  be  deeply  and  almost  irradicably  fixed  in  the  mind  of  the  average 
foreman  on  municipal  work  that  he  is  expected  to  show  his  ability 
and  skill  by  evading  or  circumventing  the  strict  requirements  of  the 
specifications  and  the  watchfulness  of  the  municipal  agents,  whatever 
his  employer  may  say  to  the  contrary.  Even  when  fairly  careful, 
honest  and  conscientious  he  may  need  friendly  oversight.  He  is 
naturally  and  properly  anxious  to  save  all  the  money  he  can  for  his 
employer,  whether  from  a  desire  to  loyally  serve  that  employer's 
interest,  or  to  enhance  his  reputation  for  doing  work  cheaply.  He 
may  not  appreciate  the  importance  of  minor  requirements  of  the 
specifications  and  may  believe  they  can  be  ignored  without  real . 
detriment  to  the  utility  of  the  completed  work.  Like  other  men  he 
may  sometimes  be  careless  or  forgetful,  however  good  his  intentions. 

These  human  qualities  are  not  confined  to  foremen  on  contract 
work.  They  are  liable  if  not  likely  to  be  found  in  the  foremen  on 
work  done  for  the  municipality  by  the  direct,  or  day's  work  system. 
They  may  be  encouraged  by  the  impression  or  belief  that  they  will 
not  be  held  by  the  municipal  authorities  to  as  strict  an  observance  or 
accountability  as  they  would  be  if  the  work  were  being  done  by  a 
contractor — which  is  too  often  true.  The  absence  of  some  of  the 
motives  of  foremen  employed  by  contractors  is,  therefore,  not  a 
sufficient  reason  for  dispensing  with  inspectors  on  work  done  by  the 
city  direct. 

It  should  be  trite  to  say  that  inspectors  should  be  chosen  with 
some  regard  to  their  qualifications  for  the  work  they  are  expected  to 
do.  One  cannot,  of  course,  expect  to  secure  experts  for  such  posi- 
tions at  the  rate  of  compensation  usually  paid;  but  it  is  reasonable 
to  require  that  an  appointee  to  such  positions  shall  possess  the  fol- 
lowing qualifications: 

That  he  shall  be  honest,  trustworthy  and  loyal. 

That  he  shall  be  a  man  of  at  least  average  intelligence  and  common 
sense. 

That  he  shall  have  some  practical  knowledge  of  or  experience  in 
the  work  he  is  employed  to  inspect. 

That  he  shall  be  a  man  of  good  personal  habits. 

That  he  shall  be  habitually  punctual,  industrious,  and  alert,  and 
shall  possess  a  fair  share  of  that  quality  commonly  called  "back- 
bone." 

It  will  not,  I  am  sure,  be  denied  that  a  very  large  number  of  the 


INSTRUCTIONS  TO  INSPECTORS        93 

inspectors  found  upon  municipal  public  work  fall  short  in  one  or  more 
of  these  qualifications. 

Inspectors  who  habitually  expect  or  accept  compensation  or  gra- 
tuities from  the  contractor  violate  the  first  requirement,  and  their 
number  is  astonishingly  large.  These  are  useless,  or  worse  than  use- 
less, to  the  municipality.  There  are  not  a  few  contractors  who  will 
take  advantage  of  the  presence  on  the  work  of  such  inspectors  to  do 
things  that  they  would  not  do  if  thrown  wholly  on  their  own  honor 
and  responsibility.  Contractors  can  hardly  be  blamed  for  expecting 
some  compensation  for  the  money  thus  exacted  or  accepted  by  the 
inspector  from  them. 

The  requirement  that  the  appointee  shall  have  some  practical 
knowledge  of  and  experience  in  the  work  he  is  expected  to  do, 
while  often  disregarded,  is  of  real  importance.  Good  workmanship 
embraces  many  small  details  that  are  essential,  and  inferable  from 
the  specifications,  but  cannot  be  stated  at  length  therein,  and  the 
inspector  should  have  a  good  working  knowledge  of  these. 

Unfortunately,  large  numbers  of  inspectors  are  employed  for 
personal  or  political  reasons,  or  because  more  competent  men  are 
not  available.  They  know  little  or  nothing  from  practical  knowledge 
and  experience  about  the  work  they  are  assigned  to  inspect.  Effi- 
cient service  cannot  be  expected  from  such,  even  if  they  possess 
the  other  necessary  qualifications.  The  obvious  remedy,  where  a 
sufficient  number  of  qualified  inspectors  cannot  be  obtained  at 
call,  would  be  to  train  up  a  permanent  force  by  having  the  promising 
tyros  serve  a  sufficient  apprenticeship  under  older  and  more  experi- 
enced inspectors;  but  this  is  seldom  done. 

Inspectors,  whether  appointed  by  the  engineer  in  charge  or  not, 
should ,  be  absolutely  under  his  control,  including  the  power  of 
dismissal  without  unnecessary  formalities.  Where  they  are  under 
civil  service  regulations  and  can  be  dismissed  only  upon  charges 
and  after  a  hearing  before  some  third  person,  the  obstacles  in  the 
way  of  promptly  getting  rid  of  an  incompetent  or  unfaithful  inspector 
are  often  so  great  as  to  be  discouraging  if  not  deterrent.  He  may 
be  clearly  below  a  reasonable  standard  of  honesty  or  efficiency  but 
it  may  be  very  difficult  to  formulate  distinct  charges  and  support 
them  with  positive  evidence.  Thus,  one  may  be  morally  certain 
that  an  inspector  is  accepting  gratuities  from  a  contractor,  but 
unable  to  prove  it  by  legal  evidence.  If  in  such  cases  the  judgment 
and  integrity  of  the  responsible  engineer  cannot  be  trusted,  he  is 
not  fit,  himself,  for  the  position  he  occupies. 


94  STREET  ROA  DWA  Y  PA  VEMENTS 

The  question  of  how  much  authority  and  power  shall  be  given 
to  the  inspector  is  always  a  troublesome  one.  If  he  be  too  much 
limited  or  restricted,  he  cannot  properly  discharge  his  duties  or 
command  the  necessary  respect  from  the  contractor  and  his  employ- 
ees; if  he  be  given  too  much  authority  and  is  disposed  to  be  arbitrary 
or  unreasonable,  the  contractor  may  be  unjustly  treated.  So  far 
as  the  definite  requirements  of  the  specifications  are  concerned  there 
can  usually  be  no  room  for  going  astray,  but  in  the  numberless 
little  details  not  specifically  covered  in  the  specifications,  or  where 
their  language  and  intent  is  not  clear,  differences  and  disputes  may 
result  which  require  a  degree  of  knowledge  and  judgment  that  the 
inspector  may  not  possess,  and  where  his  decisions  might  be  against 
the  interests  of  the  municipality  or  unjust  to  the  contractor.  In 
such  cases  the  matter  should  always  be  referred  to  the  engineer 
or  his  assistant. 

Where  inspectors  are  employed  upon  work  done  directly  by  the 
municipality  the  relation  between  them  and  the  superintendent 
or  foreman  should  be  clearly  defined  and  understood.  Briefly 
stated,  this  relation  should  be  the  same  as  that  between  the  inspector 
and  the  contractor  on  contract  work. 


INSTRUCTIONS  FOR  THE  GUIDANCE  OF  INSPECTORS 
ON  STREfcT  PAVING  AND  INCIDENTAL  WORK 

GENERAL 

1.  The  chief  duty  of  the  inspector  is  to  see  that  the  work  to  which 
he  is  assigned  shall  be  carried  out  in  full  and  strict  accordance  with 
the  plans  and  specifications  therefor,   and  with  such  additional 
instructions  as  may  from  time  to  time  be  given  by  the  engineer. 

2.  These  instructions  are  intended  to  supplement  but  in  no  case 
to  take  the  place  of  the  specifications  for  the  work,  which  must  be 
fully  and  strictly  complied  with,  unless  they  are  changed  or  modified 
by  the  engineer. 

3.  Wherever  the  words  "the  engineer"  are  used  in  these  instruc- 
tions they  refer  to  the  chief  engineer  in  charge  of  the  work  for  the 
municipality,  or  his  authorized  deputies  or  agents. 

Wherever  the  words  "the  lontrattor"  are  used  they  refer  to  the 
person,  or  firm,  or  corporation  under  contract  to  perform  the  work 
to  which  you  are  assigned,  or  his  agents  or  employees  engaged  upon 
the  work. 


INSTRUCTIONS  TO  INSPECTORS  95 

4.  You  will  report  to  and  be  under  the  exclusive  direction  and 
control  of  the  engineer. 

5.  Upon  being  assigned  to  any  work  you  will  obtain  copies  of 
the  plans  and  specifications  under  which  it  is  to  be  done,  and  will 
carefully  read  and  acquaint  yourself  with  all  their  provisions  and 
requirements.     If  any  part  of  these  plans  and  specifications  are  not 
clearly  understood  by  you,  you  will  ask  the  engineer  for  explanations 
and  instructions,  and  will  be  governed  thereby.     Failure  to  under- 
stand or  to  be  familiar  with  the  plans  and  specifications  will  in  no 
case  be  accepted  as  an  excuse  for  not  complying  with  and  enforcing 
them. 

You  will  also  obtain,  study  and  familiarize  yourself  with  all  the 
blank  forms,  reports,  etc.,  that  are  to  be  used  by  you  on  the  work, 
so  that  they  may  be  correctly  utilized;  you  will  also  obtain  a  proper 
supply  of  such  apparatus,  tools,  stationery,  etc.,  as  you  will  need 
upon  the  work. 

6.  In  inspecting  any  work  done  under  contract  you  are  to  assume 
that  the  contractor  is  bound  to  carry  out  in  good  faith  the  plans  and 
specifications  attached  to  his  contract,  and  that  he  may  be,  and  must 
be,  held  to  a  strict  compliance  with  them  unless  you  receive  instruc- 
tions to  the  contrary  from  the  engineer.     You  will  be  held  responsi- 
ble for  the  enforcement  of  these  plans  and  specifications  so  far  as 
they  relate  to  the  doing  of  the  work. 

7.  In  case  the  contractor  or  his  agents  shall  neglect  or  refuse  to 
comply  with  the  plans  and  specifications  or  to  perform  the  work  in 
a  proper  manner,  or  in  accordance  with  the  instructions  of  the  engi- 
neer, you  will  direct  him  to  suspend  the  particular  work  in  fault 
and  will  report  all  the  facts  promptly  to  the  engineer  and  await  his 
instructions,  which,  when  received,  you  will  proceed  to  enforce. 

8.  You  will  be  expected  to  be  upon  the  work  at  all  times  when 
work  is  in  progress,  whether  during  ordinary  working  or  office  hours, 
or  not.     But  in  case  the  contractor  shall  work  continuous  day  and 
night  forces,  or  otherwise  so  conduct  the  work  as  to  require  the  pres- 
ence of  an  inspector  for  unusual  or  unreasonable  hours  of  service, 
you  will  notify  the  engineer  and  ask  instructions  or  assistance.     If 
for  any  reason  you  are  to  be  unable  to  be  present  whenever  work  is 
in  progress  you  will  promptly  notify  the  engineer  in  time  to  enable 
him  to  supply  a  substitute. 

9.  All  reports  and  records  required  of  you  by  the  engineer  must 
be  promptly  made  up  and  forwarded  to  him  at  the  time  and  in  the 
manner  he  may  direct.     You  will  promptly  acknowledge  in  person 


96  STREET  ROADWA  Y  PA  VEMENTS 

or  writing  any  instructions  received  from  the  engineer  and  in  case 
such  instructions  are  not  clearly  understood  by  you,  you  will  ask 
for  explanation  or  advice. 

You  will  keep  a  notebook  or  diary  in  which  all  occurrences  or 
matters  of  interest  relating  to  the  work  will  be  recorded  each  day, 
which  book  will  be  delivered  to  the  engineer  on  the  completion  of 
the  work,  or  whenever  your  connection  therewith  may  end.  All 
diaries,  notebooks  and  records  kept  on  the  work  are  the  property 
of  the  city. 

10.  While  your  first  duty  is  to  see  that  the  work  is  done  in  accord- 
ance with  the  plans  and  specifications,  you  will,  so  far  as  consistent 
with  this  duty,  be  considerate  of  the  interests  of  the  contractor  and 
facilitate  his  work  as  much  as  practicable.     Materials  should  be 
inspected  promptly  upon  delivery  and  in  such  a  manner  as  not  to 
delay  or  discommode  the  contractor  more  than  is  necessary.     Errors, 
defects  or  delinquencies  in  the  work  should  be  detected  and  called 
attention  to  promptly,  so  as  to  avoid  tearing  up  and  re-construction 
as  far  as  practicable. 

11.  Orders  and  instructions  should  be  given  to  the  contractor  or 
his  foremen  or  representatives  on  the  work  and  not  to  the  laborers, 
unless  in  urgent  cases. 

12.  You  shall  not  at  any  time,  before,  during,  or  after  the  comple- 
tion of  the 'work,  ask  or  accept  from  the  contractor  or  any  of  his 
agents  or  employees,  or  from  any  other  person  whom  you  may  have 
reason  to  believe  is  acting  for  the  contractor,  any  money,  gifts, 
gratuities  or  other  considerations  of  value,  whether  as  compensa- 
tion for  services  rendered  him  or  otherwise.     The  penalty  for  vio- 
lation of  this  rule  will  be  dismissal  from  the  service  followed  by  such 
legal  prosecution  as  the  engineer  may  direct.     This  rule  does  not 
apply  to  the  ordinary  small  courtesies  common  between  gentlemen 
associated  in  business. 

13.  It  is  a  condition  of  your  employment  that  your  services  shall 
be  loyal  to  the  interests  of  the  municipality,  efficient,  and  satis- 
factory to  the  engineer,  and  that  whenever  in  his  opinion  your 
service  falls  short  of  this  standard  he  may  dismiss  you  at  any  time, 
without  previous  notice. 

STREET  PAVING  WORK 

14.  Sub -foundation. — The  usual  procedure  in  preparing  the  sub- 
foundation  for  a  pavement  is: 

The  removal  of  the  old  pavement  if  one  exists  on  the  street. 


INSTRUCTIONS  TO  INSPECTORS  97 

The  setting  of  new  or  the  resetting  of  the  old  curbing.  (If  con- 
crete combined  curb  and  gutter  is  used  it  is  not  constructed  until 
after  the  rough  grading  is  done.) 

The  rough  grading  of  the  street. 

The  fine  grading  of  the  street. 

In  this  work  the  main  things  for  the  inspector  to  look  aftei  are 
the  following: 

If  an  old  pavement  is  to  be  taken  up  and  any  part  of  it  is  to  be 
reserved  for  use  by  the  city,  see  that  the  material  is  not  injured  in 
handling  and  is  disposed  of  as  the  specifications  or  the  instructions 
of  the  engineer  require. 

15.  Curbing. — New  curb  stone  should  be  inspected  as  soon  as 
practicable  after  it  is  delivered  on  the  street  so  that  the  contract- 
or may  have  time  to  replace  any  that  may  be  rejected.  Rejected 
stones  should  be  plainly  marked  on  their  tops  with  red  paint,  and 
the  contractor  required  to  remove  them  from  the  street.  Stones 
that  are  defective  in  dressing  should  be  given  some  distinctive  mark 
and  the  attention  of  the  contractor  called  to  them  so  that  the 
necessary  redressing  may  be  done  well  in  advance  of  the  setting, 
and  reinspected. 

If  the  old  curb  stone  is  to  be  redressed  and  reset,  it  should  be 
inspected  as  soon  as  possible  after  it  is  taken  out  and  all  stones  that 
are  not  suitable  for  re-use  rejected  and  removed  from  the  work. 
The  redressing  of  the  stones  should  be  looked  after  carefully.  The 
tendency  in  this  work  is  toward  the  use  of  old  stones  that  do  not, 
or  cannot  be  made  to  comply  with  the  specifications,  and  toward 
laxity  in  the  dressing. 

Setting  Curbing. — In  the  setting  of  curbing  the  points  to  be 
looked  after  are: 

To  see  that  the  trenches  are  excavated  to  the  full  dimensions  so 
as  to  provide  space  for  the  use  of  the  full  quantity  required  of  con- 
crete, gravel  or  broken  stone  in  which  the  curb  is  to  be  embedded. 

To  see  that  the  stones  are  set  to  true  grade  and  alignment. 

That  the  concrete,  gravel  or  crushed  stone  used  is  of  the  proper 
quality,  the  proper  quantity  used,  and  that  it  is  placed  and  com- 
pacted so  as  to  fill  the  spaces  designated  under  and  around  the 
stone.  The  tendency  of  the  workmen  is  to  treat  these  details  as 
unimportant  and  to  slight  the  work. 

After  the  curbing  is  set  any  spaces  between  it  and  the  edge  of  the 
sidewalk  are  to  be  cleaned  out,  filled  and  trimmed  with  Portland 
cement  mortar. 


98  STREET  ROA  DWA  Y  PA  VEMENTS 

16.  Rough  Grading. — If  plows  and  scrapers  are  used  in  the  rough 
grading,  see  that  they  are  not  allowed  to  penetrate  or  to  disturb 
the  natural  soil  below  the  true  grade,  and  to  prevent  this  it  is  better 
to  require  that  the  plowing  and  scraping  shall  not  approach  nearer 
than  one  or  two  inches  to  the  true  grade. 

If  embankment  or  rilling  is  necessary,  the  filling  material  must 
be  deposited  in  regular  layers  not  more  than  six  inches  deep  and 
each  layer  must  be  well  compacted  by  rolling  or  ramming  before 
the  next  layer  is  applied. 

17.  Fine  Grading. — The  fine  grading  (with  pick  or  mattock  and 
shovel),  to  bring  the  sub-grade  to  the  true  grade  and  contour  re- 
quired, should  be  done  with  reasonable  accuracy  and  care.     Allow- 
ance must  be  made  for  compression  under  the  roller,  so  that  when 
completed  the  surface  shall  not  vary  more  than  half  an  inch  below 
nor  more  than  a  quarter  of  an  inch  above  the  true  grade,  in  order 
that  room  for  the  full  thickness  of  concrete  foundation  may  be  pro- 
vided, and  no  more.     Humps,  depressions  and  irregularities  of  the 
surface  are  to  be  avoided.     The  fine  grading  will  be  completed  by 
thoroughly  rolling  or  tamping  the  surface  to  make  the  soil  firm  and 
dense.     On  some  soft  or  wet,  clayey  soils,  excessive  rolling  may  pro- 
duce a  plastic  or  "liver-like"  condition  and  the  rolling  should  be 
discontinued  where  such  a  tendency  appears. 

18.  Work  Incidental  to  Grading. — Where  it  is  a  part  of  the  con- 
tractor's work  to  reconstruct  or  readjust  catch-basins,  manholes, 
covers,  and  other  structures,  he  should  be  required  to  keep  this 
work  done  well  in  advance  of  the  laying  of  the  concrete  founda- 
tion.    If  this  work  is  delayed  until  after  the  main  body  of  the  con- 
crete is  in  place,  leaving  openings  to  be  filled  later,  hurriedly  and 
perhaps  carelessly,  it  may  result  in  weak  patches  in  the  concrete 
around  these  structures,  where,  in  fact,   the   concrete   should  be 
strongest. 

CONCRETE  FOUNDATIONS 

19.  The  concrete  foundation  of  a  pavement  is  a  most  important 
part  of  the  work,  and  must  not  be  slighted  in  any  way. 

20.  Quality  of  Materials. — The  quality  of  the  materials  used  for 
making  the  concrete  are  fully  described  in  the  specifications,  and  they 
must  be  substantially  and  uniformly  adhered  to. 

The  Portland  cement  delivered  on  the  street  will  presumably  have 
been  previously  inspected  and  accepted  by  the  engineer,  but  any 
change  in  the  kind,  or  brand,  or  apparent  quality  of  the  cement  de- 


INSTRUCTIONS  TO  INSPECTORS  99 

livered  after  the  beginning  of  the  work  should  not  be  permitted  with- 
out the  approval  of  the  engineer.  Barrels  or  bags  of  cement  not 
plainly  marked  with  the  brand,  or  name  of  the  manufacturer  must  be 
rejected.  You  will  frequently  make  balls  of  stiff  mortar  from  the 
cement  and  sand  used  (i  part  cement,  2  parts  sand)  and  set  them 
aside  for  observation.  If  in  eight  hours  these  balls  do  not  set  up 
hard  the  fact  should  be  promptly  reported  to  the  engineer. 

The  sand  and  stone  will  naturally  vary  slightly  from  time  to  time, 
but  should  not  differ  materially  from  the  requirements  of  the  speci- 
fications or  the  standards  adopted  by  the  engineer.  Stone  or  gravel 
that  contains  any  considerable  quantity,  say  more  than  5%,  of 
foreign  matter,  such  as  soil  or  refuse,  should  be  rejected.  Stone 
containing  an  excessive  quantity  of  fine  fragments  or  screenings 
bunched  together  in  the  pile,  should  be  mixed  with  the  mass  of 
larger  stone  before  it  is  used,  so  as  to  produce  a  mass  of  fairly  even 
composition.  Stone  that  is  coated  with  mud,  or  that  is  not  sound 
and  hard  should  be  thrown  out. 

Sand  that  is  moderately  coarse  and  does  not  contain  more  than 
7  i/  2  %  of  clay  or  soil,  and  is  free  from  vegetable  refuse,  may  be  used. 

21.  Storing  Materials. — Cement  stored  on  the  street  must  be 
stacked  up  on  dry  lumber  floors  at  least  four  inches  from  the  ground 
and  effectually  covered  to  protect  it  from  rain  or  snow.     Packages  of 
cement  which,  when  turned  out  for  use  contain  hard  lumps  should  be 
rejected. 

Sand  and  stone  must  be  stored  on  tight  lumber  floors  to  prevent 
their  admixture,  when  being  shoveled  up,  with  street  soil  or  other 
impurities.  This  requirement  must  be  enforced. 

22.  Proportioning  Concrete. — The  proportions  of  cement,  sand 
and  stone  or  gravel  named  in  the  specifications  must  be  strictly 
adhered  to. 

A  barrel  of  Portland  cement  will  be  considered  as  four  cubic 
feet  and  a  standard  bag  of  cement  as  one  cubic  foot. 

It  is  usual  for  the  contractor  to  measure  the  sand  and  stone  by 
wheelbarrow  loads.  In  that  case  you  will  measure  and  determine 
the  capacity,  in  cubic  feet,  of  the  convenient  or  average  wheelbarrow 
load,  and  determine  the  size  and  number  of  loads  each  of  sand  and 
stone  required  for  one  batch  of  concrete  (if  made  by  hand)  and  there- 
after see  that  the  quantities  thus  determined  are  used,  and  the  wheel- 
barrow loading  uniform.  To  measure  the  contents  of  a  wheel- 
barrow load,  use  a  square  box  holding  one  cubic  foot.  It  cannot  be 
accurately  measured  on  the  barrow. 


1 00  STREET  ROA DWA  Y  PA  VEMENTS 

As  a  check  upon  the  proportioning  of  materials,  you  should  occa- 
sionally keep  a  record  of  the  quantities  of  cement,  sand  and  stone 
used  for,  say,  one  or  two  hours,  and  mark  and  measure  up  the  quan- 
tity of  concrete  made  with  them,  and  from  this  data  compute  the 
ratios  of  the  materials  used.  (In  ordinary  street  concrete,  propor- 
tioned 1:3:6,  the  volume  of  rammed  concrete  made  will  just  about 
equal  the  volume  of  the  stone  used.) 

Where  the  concrete  is  mixed  by  a  machine  with  automatic  feeding 
devices,  reliance  must  not  be  placed  upon  the  machine  for  proper 
proportioning.  Frequent  tests  of  the  materials  used  and  the  volume 
of  concrete  turned  out  should  be  made  as  described  above,  and  any 
necessary  corrections  made  in  the  feeding  devices  of  the  machine. 
This  test  should  be  made  daily  if  practicable.  The  eye  will  usually 
detect  any  material  change  in  the  composition  of  the  concrete,  and 
whenever  such  changes  are  observed  the  composition  ought  to  be  at 
once  checked  up  by  measurement. 

23.  Mixing  Concrete. — See  that  the  specifications  are  followed. 
Use  sufficient  water  to  make  what  is  commonly  called  a  wet  con- 
crete but  not  so  wet  that  free  water  will  drain  from  the  mixed  batch 
before  ramming.     The  test  for  proper  mixing  will  be  that  all  the 
fragments  of  stone  are  completely  covered  with  mortar. 

24.  Placing  Concrete  on  Street. — All  concrete  must  be  placed 
and  rammed  before  it  begins  to  stiffen  or  set.     Concrete  should  be 
so  handled  that   the  mortar  will   segregate  or  separate  from  the 
stone  as  little  as  possible.     When  in  place  on  the  street  it  should 
make  a  mass  of  uniform  consistency  and  appearance.     The  concrete 
should,  as  soon  as  placed  on  the  street,  be  graded  to  a  proper  thick- 
ness and  surface,  and  then  well  compacted  by  ramming.     Insist 
on  good  ramming;  this  part  of  the  work  is  not  often  properly  done. 
The  surface  of  the  concrete  should  be  brought  to  the  true  grade 
by  proper  grading  and.  tamping.     Where  necessary  to  raise  the 
surface,  additional  concrete,  made  of  small  stone,  may  be  applied 
during  the  tamping.     Neat  mortar  should  not  be  used  for  this 
purpose.     Sweeping  mortar  over  the  surface  with  street  brooms 
should  not  be  permitted — it  is  useful  only  to  cover  up  defects  and 
to  produce  an  extra  smooth  surface  (which  is  not  usually  desirable). 
To  measure  the  thickness  of  the  bed  of  concrete,  lay  a  straight-edge 
upon  the  surface  with  the  end  of  the  straight-edge  projecting  a 
foot  or  two  beyond  the  edge  of  the  concrete,  and  measure  the  space 
from  the  lower  edge  of  the  straight-edge  down  to  the  sub-foundation. 

Care  must  be  taken  to  finish  the  surface  of  the  completed  concrete 


INSTR UCTIONS  TO  INSPECTORS    '< .  < 

at  the  proper  distance  below  and  truly  parallel  to  the  grade  and  con- 
tour of  the  finished  pavement.  This  is  more  important  in  the  case 
of  sheet  asphalt  pavements,  since  irregularities  in  the  concrete  will 
cause  variation  in  the  thickness  of  the  finished  asphalt  surface, 
which  will  affect  the  durability  of  the  pavement.  The  grade 
stakes  for  the  concrete  should  therefore  be  carefully  set  and  worked 
to,  and  humps  or  depressions  between  the  stakes  should  be  avoided. 

25.  In  hot,  dry,  weather  the  concrete  must  be  kept  damp  by 
watering  it  until  it  is  at  least  five  days  old,  and  horse-travel  over  it 
must  be  prohibited  until  it  has  set  up  hard  enough  not  to  be  injured 
thereby. 

26.  Old  Paving  Stone  Foundations. — If  a  foundation  is  to  be 
made  of  old  paving  stone  blocks  reset,  the  important  points  to  be 
looked  after  are, 

The  preparation  of  the  sub-foundation. 

The  sand  bed. 

The  setting  of  the  blocks. 

The  grouting  of  the  blocks. 

The  sub-foundation  should  be  prepared,  where  necessary,  as 
stipulated  in  Sects.  16  and  17  of  these  instructions.  This  part  of 
the  work  is  likely  to  be  carelessly  done  unless  proper  work  is  insisted 
upon. 

The  sand  used  as  a  cushion  course  must  be  of  good  quality  and 
reasonably  clean.  The  use  of  mixed  sand  and  soil  taken  from  the 
street  excavation  should  not  be  permitted. 

The  blocks,  after  being  cleaned  from  adhering  dirt,  should  be 
set  with  reasonable  care,  well  bedded  in  the  sand  cushion,  and  laid 
at  such  an  elevation  below  the  completed  pavement  surface,  that 
after  being  well  rammed,  the  surface  will  be  at  the  proper  elevation 
below  the  pavement  datum. 

The  grouting  of  the  joints  is  the  most  important  part  of  the  work. 
See  that  the  mortar  is  made  and  used  in  accordance  with  the  specifi- 
cations, and  that  the  joints  are  completely  filled. 

27.  Broken  Stone  Foundations. — The   specifications  for  broken 
stone  foundations  are  sufficiently  explicit,  and  compliance  should 
be  insisted  upon.     Thorough  rolling  is  especially  important. 

SHEET  ASPHALT  PAVEMENTS 

28.  The  manufacture  of  the  mixture  for  sheet  asphalt  pavement, 
and  the  laying  of  it  on  the  street,  involve  a  number  of  separate 
elements  or  operations.     The  quality  and  durability  of  the  pave- 


1. 02  STREET  ROA  DWA  Y  PA  VEMENTS 

ment  will  depend  largely  upon  the  skill,  intelligence  and  accuracy 
with  which  each  and  all  parts  of  the  work  are  carried  out.  The 
inspector,  both  at  the  mixing  plant  and  on  the  street,  must  give 
constant  and  intelligent  attention  to  the  work.  * 

29.  Inspecting  at  Paving  Plant. — Inspectors  at  the  plant  where 
the  asphalt  paving  mixture  is  made  will  be  provided  with  the  fol- 
lowing apparatus: 

1  nest  of  standard  sieves,  Nos.  10,  30,  50,  80,  100  and  200 

2  thermometers  for  sand 

1  tank  thermometer 

2  standard  flow-plates  and  one  dozen  cartridges  for  same 
i  balance  for  weighing  sand 

6  dishes,  glass  or  porcelain,  4  inches  in  diameter. 

30.  The  more  important  things  for  the  Plant  Inspector  to  watch 
during  the  manufacture  of  asphalt  paving  mixture  are: 

a.  Quality  and  grading  of  the  sand. 

b.  Temperature  of  heated  sand. 

c.  Uniform  quality  of  the  refined  asphalt  and  flux. 

d.  Temperature  of  melted  bitumens. 

e.  Uniform  consistency  of  asphaltic  cement. 

/.  Correct  ratios  of  sand  and  asphaltic  cement. 
g.  Thorough  mixing  of  materials. 

31.  Sand. — The  general  quality  and  grain- size  of  the  sand,  re- 
quired by  the  specifications,  must  be  closely  watched  and  adhered  to. 

It  is  hardly  ever  possible  to  secure  a  natural  sand  that  will  con- 
form strictly  to  the  theoretical  composition,  but  substantial  com- 
pliance should  be  required  unless  the  Chief  Engineer  directs  other- 
wise. After  any  sand  has  been  approved  for  a  given  contract  or 
street,  all  the  sand  thereafter  used  for  that  street  should  con- 
form closely  to  the  standard  so  approved;  for  any  material  change  in 
the  quality  of  the  sand  will  change  the  quality  of  the  pavement  pro- 
duced, unless  the  proportions  of  the  other  materials  are  changed 
accordingly.  Any  material  change  in  the  sand  should  therefore  be 
promptly  reported  to  the  Chief  Engineer. 

32.  Sand  for  the  sieve  tests  should  be  taken  from  the  hot-sand 
box  and  allowed  to  become  cold.     From  the  sample  thus  taken, 
weigh  out  50  grams.     Arrange  the  nest  of  sieves  with  the  No.  200 
at  the  bottom  followed  by  Nos.  100,  No.  80,  No.  50,  No.  30  and 
No.  10  at  the  top. 

Place  the  weighed  sample  upon  the  No.  10  sieve  and  thoroughly 
shake  the  nest  until  all  the  sand  that  will,  has  passed  through  the 


INSTRUCTIONS  TO  INSPECTORS  103 

various  sieves;  then  weigh  the  various  portions,  beginning  with  that 
which  has  passed  the  No.  200  (deducting  in  each  case  the  weight  of 
the  dish).  The  portion  remaining  on  the  No.  200,  is  the  quantity 
passing  the  No.  100,  etc.  The  sum  of  all  these  portions  should  be  50 
grams,  though  it  will  usually  be  slightly  less  because  of  unavoidable 
waste.  In  use,  keep  the  sieves  clean  and  as  free  as  possible  from 
adhering  grains  by  using  a  bristle  brush. 

33.  Temperature  of  the  Sand. — The  temperature  of  the  heated 
sand  should  be  frequently  noted  by  plunging  the  thermometer  into 
the  mass.     It  should  not  fall  below  315°  F.  nor  exceed  375°  F.     It  is 
very  important  to  avoid  over-hot  sand,  because,  in  the  mixer,  the 
very  thin  films  of  bitumen  covering  the  hot-sand  grains  are  readily 
and  quickly  scorched  by  the  excessive  heat  in  the  sand. 

34.  Refined  Asphalt  and  Fluxing  Oil. — Unless  otherwise  notified 
by  the  Chief  Engineer  you  will  assume  that  the  stock  of  refined 
asphalt  on  hand  at  the  beginning  of  the  work  has  been  inspected  and 
is  satisfactory.     You  will,  however,  note  the  appearance  of  the 
material  and  the  character  and  marking  of  the  barrels  or  packages, 
and  will  not  permit  the  use  of  any  new  shipments  of  materials  of 
different  appearance  or  brand  without  authority  from  the  Chief 
Engineer.     The  above  instructions  apply  also  to  the  oil  used  for 
fluxing. 

35.  Ratio  of  Asphalt  and  Flux. — You  will  frequently  note  and 
record  the  weight  of  asphalt  and  of  flux  used  in  charging  the  melting 
tanks. 

36.  Temperature  in  Melting  Tanks. — The  melting  kettles  are 
usually  equipped  with  fixed  thermometers,  but  their  reading  should 
be  frequently  checked  with  your  detached  tank  thermometer.     You 
will  see  that  the  temperatures  in  the  kettles  are  kept  within  the  limits 
named  in  the  specifications.     See  that  the  melted  asphaltic  cement 
is  kept  constantly  agitated  as  required  by  the  specifications. 

37.  Uniformity  of  Asphaltic  Cement. — It  is  very  important  that 
the  asphaltic  cement  shall  be  of  uniform  composition  and  consist- 
ency, or  hardness. 

When  the  composition  and  consistency  of  the  asphaltic  cement  to 
be  used  for  the  surface-course  of  any  street  has  been  determined 
upon  and  approved  by  the  engineer,  you  will  take  out  and  preserve 
a  sufficiently  large  quantity  to  be  used  thereafter  as  a  standard,  and 
each  subsequent  tank  of  cement,  before  it  is  used,  should  be  tested 
by  comparing  it  with  this  standard  in  the  following  manner,  using 
the  flow-plate  apparatus: 


104  STREET  ROADWAY  PAVEMENTS 

Melt  and  fill  two  cartridges  with  the  standard  cement,  and  two 
with  the  cement  to  be  tested,  marking  them  for  identification. 
When  cold,  carefully  remove  with  a  wetted  dull  knife  any  surplus 
cement  from  the  ends  of  the  cartridges  so  as  to  leave  them  exactly 
full  and  the  metal  ends  clean.  Immerse  them  in  cold  water  until 
they  are  all  of  the  same  temperature.  Then  place  and  fasten  these 
filled  cartridges  on  the  grooved  plate  with  their  lower  ends  exactly 
to  the  zero  line  on  the  plate,  the  standard  samples  alternating  with 
the  new.  Then  place  the  plate,  at  an  inclination  of  about  45°,  in 
front  of  a  source  of  uniformly  distributed  heat,  as,  for  instance,  near 
a  steam  boiler  or  large  steam  pipe,  or  (when  the  weather  is  favorable) 
in  the  sunshine,  facing  the  sun.  Leave  the  plate  in  this  position  until 
the  bitumen  in  the  cartridges  shall  have  melted  and  flowed  down 
the  grooves  an  average  of  from  four  to  five  inches.  Then  measure 
the  lengths  of  flow  of  each  from  the  zero  line  on  the  plate.  If  the 
average  flow  of  the  new  samples  differs  more  than  5  per  cent,  from 
that  of  the  standards,  the  new  cement  should  be  regarded  as  unsat- 
isfactory and  should  be  corrected  by  adding  more  asphalt  or  flux, 
as  may  be  required. 

(If  a  penetration  apparatus  is  supplied  or  is  available,  the  pene- 
tration method  may  be  used  instead  of  this  flow-method  for  deter- 
mining the  consistency  of  the  cements.  Proper  instructions  for 
its  use  will  accompany  the  apparatus.) 

38.  Ratio  of  Sand  and  Cement. — When  the  proper  ratio  of  sand 
and  asphaltic  cement  has  been  determined  for  any  street  you  will 
see  that  this  ratio  is  carefully  adhered  to.     The  correctness  of  the 
weighing  scales  used  should  be  frequently  tested. 

39.  Mixing. — When  the  sand  and  asphaltic  cement  are  properly 
mixed  the  appearance  of  the  mass  will  be  perfectly  uniform  through- 
out, with  every  grain  of  sand  entirely  and  evenly  coated  with  cement. 
The  mixing  should,  however,  be  continued  somewhat  beyond  the 
attainment  of  this  condition,  so  as  to  insure  thoroughness.     After 
the  proper  result  has  been  arrived  at,  either  the  time  in  the  mixer, 
or  the  number  of  revolutions  of  the  mixer  shaft  should  be  noted  and 
the  standard  thus  determined  substantially  adhered  to  thereafter. 
With  the  standard  mixers  commonly  used,  the  hot  sand  and  the 
filler  (dust)  should  first  be  put  into  the  mixer  and  mixed  for  about 
fifteen  seconds;  then  the  asphaltic  cement  added  and  the  mixing 
continued  as  long  as  necessary  (in  the  usual  mixer  not  less  than  sixty 
seconds). 

40.  Records. — You  will  keep  complete  records  of  the  results  of 


INSTRUCTIONS  TO  INSPECTORS  105 

your  observations  and  tests  in  a  book  which  will  be  provided  for  the 
purpose,  and  will  make  such  reports  to  the  Engineer  as  he  may  direct. 

41.  Inspection  on  the  Street.— The  leading  things  to  be  kept  in 
mind  by  the  street  inspector,  in  the  laying  of  asphalt  pavement  on 
the  street,  are  the  following: 

a.  Temperature  of  mixtures  when  applied  to  the  street. 

b.  Proper  preparation  of  the  street  surface  before  material   is 
laid. 

c.  Laying  and  rolling  of  the  binder-course. 

d.  Laying  of  the  surface-course. 

e.  Rolling  the  surface-course. 

42.  Inspector's  Equipment. — The  inspector  will  be  supplied  with 
the  following  apparatus: 

i  armored  thermometer  reading  from  200°  F.  to  500°  F. 

i  graduated  spatula. 

i  twelve-foot  straight  edge. 

i  fifty-foot  tape  line. 

43.  Temperature  of  Mixture. — If  proper  care  has  been  taken  at 
the  mixing  plant  the  mixture  will  not  arrive  on  the  street  at  too  high 
a  temperature,  and  your  principal  care  will  be  to  see  that  it  is  not 
laid  at  too  low  a  temperature.     The  minimum  temperature  named 
in  the  specifications  should  be  adhered  to.     While  the  main  or  interior 
mass  of  a  wagon  load  may  be  well  above  that  temperature,  the  top 
and  outer  part  of  the  load  may  be,  particularly  in  cold  weather,  too 
cold  to  be  safely  used.     Some  of  this  colder  portion  may  usually  be 
sufficiently  reheated  by  mixing  it  with  the  hotter  material,  if  prop- 
erly handled  in  unloading;  but  any  material  that  is  so  cold  as  to  be 
lumpy  when  unloaded,  or,  more  particularly,  when  being  raked  out, 
should  be  discarded.     This   applies   to  both  surface  and  binder 
mixtures. 

It  must  not,  however,  be  overlooked  that  the  different  kinds 
of  asphalts  have  different  appropriate  working  temperatures,  and 
for  some  asphalts  the  minimum  temperature  named  in  the  specifica- 
tions may  be  too  low.  The  best  practical  guide  is  the  manner  in 
which  the  mixture  behaves  in  raking.  It  must  always  be  so  hot 
that  it  will,  under  the  rake,  break  up  into  a  uniform,  crumbling 
or  powdery  mass.  If  it  does  not  do  this  it  is  (unless  the  mixture  is 
excessively  rich  in  bitumen  or  improperly  compounded)  too  cold. 

44.  Preparation  of  Street  Surface. — Before  the  binder-course  is 
laid,  all  loose  material,  rubbish,  street  dirt  and  other  matter  foreign 
to  the  concrete  surface  must  be  removed  and  the  concrete  surface 


1 06  STREET  ROA DWA  Y  PA  VEMENTS 

swept,  if  necessary,  to  properly  clean  it,  with  street  brooms.  Neither 
binder  nor  surface  mixture  shall  be  laid  upon  wet  surfaces.  Before 
the  spreading  of  the  surface  mixture  on  the  binder  the  latter  must 
be  cleaned  of  all  foreign  matter  and,  if  necessary,  swept.  If  the 
binder  is  covered  with  mud  from  wagons  or  other  travel,  the  surface 
must  be  scrubbed  clean.  Any  part  of  the  binder-course  that  may 
have  become  broken  or  loosened  before  the  surface-course  is  applied 
must  be  taken  up  and  new  material  laid  in  its  place  with  the  same 
care  as  the  original. 

45.  Laying  Binder-course. — The  binder  mixture  must  be  care- 
fully spread  and  raked  to  such  thickness  that  after  being  rolled 
it  will  present  an  even,  true  surface  not  varying  more  than  one- 
fourth  inch  from  the  intended  finished  surface  of  the  binder.     The 
tendency  is  to  lay  the  binder-course  carelessly  and  to  roll  it  insuffi- 
ciently.    Nearly  the  same  care  in  raking  and  rolling  as  for  the 
surface-course,  should  be  insisted  upon.     If  the  binder  is  not  thor- 
oughly compressed  before  it  becomes  cold  it  is  likely,  in  future  hot 
weather,  to  soften  and  yield  under  heavy  travel  and  thus  to  start 
depressions  in  the  pavement  which  will  increase  with  time. 

46.  Laying  the  Surf  ace -course. — The  requirements  of  the  specifi- 
cations should  be  rigidly  enforced  in  the  laying  of  the  surface-course. 
Joints  against  a  cold  edge  of  previously  laid  surface  must  be  cut 
back  until  solid,  fully  compressed  material  of  full  thickness  is  reached, 
and  the  raw  edge  completely  but  thinly  painted  with  liquid  paving 
cement  or  pitch.     No  masses  or  fragments  of  cold  mixture,  whether 
of  binder  or  surface,  must  be  allowed  to  remain  on  the  surface  of 
the  binder  in  advance  of  the  placing  of  the  surface-course,  to  be 
covered  up  by  the  latter.     Such  cold  masses  will  not  be  compressed 
by  the  roller,  but  will  later,  under  a  hot  sun  and  heavy  tiavel, 
yield   and   start   depressions   in   the   pavement.     The   raking  out 
requires  to  be  properly  and  skilfully  done.     The  tines  of  the  rakes 
must  penetrate  to  the  binder,  so  that  the  raked  material  will  be  a 
uniform  mass  from  top  to  bottom. 

47.  Rolling. — You  will  insist  upon  the  rollers  being  placed  upon 
the  freshly  raked  surface  just  as  soon  as  the  material  will  bear  them 
without  being  squeezed  out  or  displaced  laterally.     The  tendency 
is  to  keep  the  rollers  off  too  long,  thus  permitting  the  chilling  of 
the  surface  and  preventing  its  proper  compression.     Do  not  take 
the  contractor's  word  as  to  how  soon  the  rolling  may  be  begun, 
but  have  trials  made  until  you  are  able  yourself  to  judge.     The 
rolling  by  the  heavy  roller  should  be  very  thorough:  keep  the  roller 


INSTRUCTIONS  TO  INSPECTORS       107 

at  work  constantly  until  the  surface  is  too  cold  to  be  impressed. 
In  operating  the  roller  lengthwise  of  the  street  begin  at  the  gutters 
and  work  toward  the  center  of  the  street.  Cross  rolling  and  diagonal 
rolling  must  be  insisted  upon  wherever  the  width  of  the  street  will 
permit  it. 

48.  Proper  Thickness  and  Surface. — While  the  completed  surface 
is  still  warm  enough  to  permit  it,  measure  the  thickness   of  the 
surface-course  by  forcing  the  graduated  spatula  through  it  to  the 
binder  and  noting  the  depth  of  penetration.     Also  test  the  trueness 
of  the  finished  surface  with  the  straight-edge,  and  if  found  defective 
in  either  thickness  of  pavement  or  trueness  of  surface,  insist  on  more 
careful  grading  and  raking  on  the  further  work. -  Try  the  completed 
gutters  with  water  to  see  that  they  are  so  truly  laid  that  puddles 
of  water  will  not  stand  in  them. 

49.  Asphalt  surface  must  not  be  laid  when  rain  or  snow  is  falling, 
or  so  long  as  the  street  surfaces  are  wet.     Surface  mixture  raked  out 
and  caught  in  a  shower  before  it  is  well  enough  rolled  to  exclude 
water  must  be  taken  up  and  discarded. 

Unless  unavoidable,  neither  binder  nor  surface  should  be  laid 
when  the  street  surface  or  the  air  is  below  40°  F.  As  a  rule,  the  lower 
the  temperature  the  of  air  the  greater  is  the  care  necessary  to  properly 
lay  asphalt  pavement. 

50.  Measure  each  day  the  area  of  pavement  laid  and  record 
that,  and  the  quantity  (number  of  batches)  of  surface  mixture  used, 
and  note  any  lack  of  uniformity  in  the  area  laid  per  batch. 

ASPHALT -BLOCK  PAVEMENT 

51.  You   may   assume,    unless   otherwise   instructed,    that    the 
Engineer  has  inspected  and  approved  the  general  character  of  the 
blocks  already  delivered  for  the  work,  unless  their  inferiority  be 
obvious,  but  you  will  be  expected  to  observe  them  carefully  as  laid 
and  to  reject  blocks  that  vary  in  dimensions  from  those  permitted  by 
the  specifications,  and  those  that  are  broken,  disfigured  or  injured. 
But  during  the  progress  of  the  work  you  will  note  the  character  of 
subsequent  deliveries  and  report  to  the  Engineer  any  apparent  change 
in  the  quality  of  the  blocks. 

The  more  important  points  to  look  after  in  the  laying  of  the 
asphalt  blocks  are:  the  quality  and  grading  of  the  mortar  bed  in 
which  the  blocks  are  set,  and  the  care  and  accuracy  of  the  block 
setting.  The  mortar  must  be  of  cement  and  sand  in  the  ratios  specified, 


1 08  STREET  ROA  DWA  Y  PA  VEMENTS 

and  sufficient  water  used  to  make  a  medium  stiff  mortar;  the  use  of 
merely  moistened  powder  must  not  be  permitted;  and  any  mortar 
that  has  begun  to  set  up  before  the  blocks  are  laid  and  rammed  must 
be  discarded. 

52.  In  setting  the  blocks  the  principal  requisites  are:  that  they  be 
well  bedded  in  the  mortar ;  that  they  be  set  so  that  after  ramming  their 
tops  will  be  accurately  in  the  pavement  datum;  that  they  be  set  and 
pressed  as  closely  together  as  possible,  levers  or  mauls  being  used  to 
force  them  into  close  contact,  both  at  ends  and  sides. 

GRANITE-BLOCK  PAVING 

53.  Assuming  that  the  foundation  has  been  properly  constructed, 
the  more  important  things  for  the  inspector  to  look  after  are : 

a.  The  quality  and  shape  of  the  blocks. 

b.  The  sand  cushion. 

c.  The  setting  of  the  blocks. 

d.  The  ramming  of  the  blocks. 

e.  The  filling  of  the  joints. 

54.  The  Blocks. — Assuming  that  the  general  quality  of  the  granite 
has  been  approved,  you  will  need  only  to  observe  and  reject  blocks 
made  from  soft  or  weathered  or  otherwise  defective  stone.     Any 
material  divergence  of  the  blocks  from  the  correct  form  or  from  the 
sizes  specified  as  permissible  will  be  readily  caught  by  the  eye  as  they 
are  brought  to  the  street,  and  they  can  then  be  thrown  out.     The 
proper  dressing  of  the  blocks  is  important  and  should  be  watched 
carefully.     While  you  are  not  expected  to  examine  each  individual 
block,  close  observation  of  the  blocks  as  they  are  handled  and  laid 
will  enable  you  to  detect  and  reject  those  that  are  materially  defec- 
tive in  shape  or  dressing;  or  excessively  wide  joints  will  call  attention 
to  these  defects  as  the  blocks  are  set. 

55.  Sand  Cushion. — The  sand  used  for  the  cushion  bed  should  be 
moderately  coarse  and  must  be  fairly  clean  and  pure.     The  tendency 
with  contractors  is  to  use  any  dirty  sand  or  sandy  loam  available  on 
the  street.     Such  material,  especially  if  it  becomes  filled  with  water, 
will  yield  under  the  blocks  and  will  not  support  them  properly.     The 
sand  bed  should  not  vary  materially  in  thickness.     It  should  be  laid 
and  graded  not  more  than  fifty  nor  less  than  twenty  feet  in  advance 
of  the  setting  of  the  blocks. 

56.  Setting  of  the  Blocks. — The  blocks  should  be  delivered  in 
front  of  the  block  setters  on  the  blocks  already  set.     The  blocks 
must  be  set  in  straight  courses  from  curb  to  curb  the  courses  running 


INSTRUCTIONS  TO  INSPECTORS       109 

at  right  angles  to  the  street  (except  at  street  intersections).  All 
the  blocks  in  any  one  course  must  be  of  the  same  width.  Each  block 
should  be  so  set  that  the  whole  of  its  bed  will  be  seatedjipon  sand. 
The  usual  practice  of  block  setters  is  to  make  a  bed  by  drawing  the 
sand  into  a  small  ridge  upon  which  the  outer  edge  of  the  block  is 
rested,  its  weight  canting  it  against  the  course  already  laid.  This 
usually  leaves  a  cavity  under  the  back  edge  of  the  block  which  neither 
the  subsequent  joint  filling  or  ramming  closes  up,  so  that  the  block 
may  rest  permanently  on  only  a  part  of  its  bed.  The  practice  is  so 
fixed  with  block  setters  that  it  will  require  firmness  and  persistency 
to  prevent  it,  but  you  should  insist  that  it  be  so  modified  as  to  give 
a  solid  bearing  for  each  block  over  its  whole  base. 

The  blocks  must  be  set  solidly  against  each  other  so  as  to  make 
the  joints  of  the  least  possible  width.  Unless  close  attention  is 
given  to  this  the  joints  are  likely  to  greatly  exceed  the  width  per- 
mitted by  the  specifications.  Care  should  be  taken  that  the  blocks 
are  set  truly  vertical  so  that  their  upper  face  shall  be  parallel  to  the 
plane  of  the  street.  In  setting  the  blocks  their  straightest  and 
truest  face  should  be  placed  upward  so  as  to  make  the  surface  of  the 
pavement  as  smooth  and  even  as  possible.  Block  setters  are  often 
careless  about  this. 

Ordinarily  no  grade  stakes  are  set  for  the  surface  of  the  pavement 
and  templates  are  seldom  used,  the  block  setters  using  only  their  eyes 
to  make  the  surface  conform  to  the  intended  contour  of  the  street. 
This  usually  results  in  the  completed  street  being  more  or  less  wavy 
and  irregular,  and  in  a  lack  of  regular  and  uniform  cross-section  in 
different  parts  of  the  street,  often  very  perceptible  to  the  eye. 
Care  should  be  taken  to  avoid  this  as  much  as  possible.  Straight- 
edges and  templates,  cut  to  the  proper  curve  for  the  surface,  should 
be  provided  and  used. 

57.  Ramming  the  Blocks. — This  part  of  the  work  is  likely  to 
be  slighted  unless  carefully  watched.  The  important  thing  is  to 
have  each  block  equally  and  sufficiently  rammed  to  bring  it  to  a 
firm  bearing  on  the  sand,  as  well  as  to  bring  its  top  to  the  proper 
grade.  The  rammers  will  be  disposed  to  touch  lightly  blocks  or 
areas  which  if  thoroughly  rammed  would  be  driven  below  the  true 
surface  of  the  pavement,  and  subsequent  travel  may  force  these 
down,  making  depressions  in  the  surface.  It  is  a  very  common 
practice  for  the  men  working  the  rammers  to  shirk  on  this  work  by 
allowing  the  rammers  to  fall  with  little  more  force  than  that  due  to 
their  own  weight.  This  should  be  detected  and  remedied. 


110  STREET  ROA  DWA  Y  PA  VEMENTS 

58.  Filling  the  Joints. — The  specifications  are  quite  full  and  clear 
regarding  this  part  of  the  work  and  little  further  need  be  said. 

Care  is  necessary,  whether  the  joints  be  filled  with  gravel  and 
bituminous  cement  or  with  grout,  to  secure  the  complete  filling  of 
all  the  joints.  If  the  weather  is  cold  at  the  time  the  work  is  done, 
the  gravel  filling  may  become  so  chilled  before  the  bituminous 
cement  is  poured  that  it  will  not  flow  to  the  bottom  of  the  joints. 
For  this  reason  it  is  important  that  the  cement  be  worked  at  the 
highest  temperature  that  it  will  bear  without  injury. 

If  grout  filling  is  used  care  is  necessary  to  make  the  mortar  of 
the  right  consistency.  If  too  thick  it  will  not  flow  freely  to  the  bot- 
tom of  the  joint;  if  too  thin  its  strength  will  be  materially  reduced. 
Experiments  should  be  made  to  determine  the  proper  consistency, 
and  when  this  is  found,  the  quantity  of  water  used  in  making  the 
mortar  should  be  determined  and  thereafter  measured  out  for  each 
batch. 

The  mortar  must  be  kept  constantly  stirred  until  used,  otherwise 
the  sand  is  likely  to  settle  to  the  bottom.  Whatever  filling  is  used, 
a  second  and  sometimes  a  third  pouring  will  be  necessary  to  com- 
pletely fill  the  joints. 

BRICK  PAVEMENT 

59.  The  matters  requiring  most  attention  in  the  construction  of 
brick  pavement  (assuming  that  the  foundation  is  in  place)  are  the 
character  and  quality  of  the  brick,  the  sand  cushion,  the  setting  of 
the  brick,  and  the  filling  of  the  joints  between  the  brick. 

60.  Inspecting  the  Brick. — The  examination,  testing  and  accept- 
ance, in  a  general  way,  of  the  brick  to  be  used  for  the  work  will 
be  made  in  the  engineer's  office,  and  your  duty  will  be  confined  in 
this  matter  to  seeing  that  the  brick  delivered  and  used  are  in  accord- 
ance with  the  standard  established  and  the  general  requirements 
of  the  specifications.     You  can  best  inspect  the  brick  as  they  are 
being  laid  or  after  they  have  been  laid,  and  before  the  surface  has 
been  rammed  or  rolled.     Presumably  the  brick-setters  will  discard 
most  of  the  unsuitable  brick  during  the  progress  of  their  work, 
particularly  if  they  are  given  to  understand  distinctly  the  defects 
that  will  cause  rejection. 

As  the  setting  is  completed,  go  carefully  over  the  surface  of  the 
pavement  and  mark  plainly  all  the  bricks  that  are  to  be  removed 
for  defects  and  see  that  all  such  are  taken  out  and  replaced  with 


INSTRUCTIONS  TO  INSPECTORS  111 

good  brick.  The  principal  defects  that  should  be  observed  are: 
soft  or  underburned  bricks;  those  that  are  warped  or  deformed 
so  that  they  will  not  fit  closely  to  their  neighbors,  or  have  warped 
or  ill -shaped  tops;  those  that  are  broken  or  chipped  or  show  injurious 
cracks,  and  those  that  are  perceptibly  wider  or  narrower  than  their 
neighbors  in  the  same  course. 

Soft  or  underburned  brick  may  be  detected  with  most  certainty 
by  having  the  contractor  wet  the  surface  of  the  pavement  by 
sprinkling.  The  soft  brick  will  absorb  more  water  and  remain 
damp  longer  than  the  hard  brick  and  can  thus  be  readily  detected. 
This  test  can  be  applied,  however,  only  to  pavements  the  joints  of 
which  are  to  be  filled  with  grout,  as  bituminous  filling  should  not 
be  applied  to  brick  with  wet  surfaces,  and  to  wait  until  they  become 
dry  after  the  wetting  would  delay  the  work  unwarrantably. 

61.  Sand  Cushion. — See  that  the  sand  used  is  free  from  foreign 
matter  and  pebbles,  as  required  by  the  specifications,  and  that  the 
sand-bed  is  of  uniform  thickness,  correctly  gaged,  and  rolled  to  the 
true  plane  of  the  pavement,  additional  sand  being  added  or  surplus 
removed  where  necessary  to  secure  this  result.     See  that  the  cushion 
is  not  thereafter  disturbed  or,  if  disturbed,  that  it  be  restored  to 
its  original  condition. 

62.  Setting  the  Brick. — The  bricks  are  to  be  set  as  closely  together 
as  possible  both  at  sides  and  ends,  so  that  the  joints  will  not  be  wider 
than  permitted  by  the  specifications.     Where  the  bricks  have  lugs 
or  letters  on  one  side,  the  lug-sides  shall  in  no  case  be  laid  together. 
The  courses  must  be  reasonably  straight  entirely  across  the  street. 
See  that  the  bricks  in  adjoining  courses  break  joint  not  less  than 
three  inches.     Brick-setters  are  likely  to  be  careless  about  this. 
Do  not  permit  bats  to  be  used  except  where  necessary  at  the  ends 
of  courses  or  to  fit  the  pavement  against  street  railroad  rails  or  around 
manholes  or  other  structures  in  the  street,  and  insist  that  this 
filling  in  shall  follow  immediately  after  the  brick-setting,  and  that 
close  fits  shall  be  made. 

63.  Rolling  the  Pavement  Surface. — This  should  be  carefully 
and  uniformly  done  so  as  to  insure  the  even  surface  and  contour 
of  the  pavement.     Do  not  allow  the  roller  to  make  sharp  turns 
on  the  freshly  laid  brick  surface  as  it  will  disturb  and  cant  the 
loose  brick.     The  roller  should  run  back  onto  the  fully  completed 
pavement  to  make  any  necessary  turns  or  considerable  changes  of 
direction.     Quick  starts  or  stops  of  the  roller  on  the  fresh-laid  brick 
should  be  avoided  for  the  same  reason. 


112  STREET  ROADWA  Y  PA  VEMENTS 

64.  Filling  the  Joints. — Whether  grout  or  bituminous  filling  be 
used  the  important  thing  is  to  get  all  the  joints  completely  filled. 
Where  bituminous  cement  is  used,  if  the  work  is  done  in  very  cool 
weather  the  brick  is  likely  to  chill  the  cement  before  it  reaches  the 
bottom  of  the  joints  unless  the  cement  be  applied  as  hot  as  possible 
without  injuring  it,  and  the  pouring  be  rapidly  and  carefully  done. 

If  grout  filling  be  used,  see  that  the  mortar  is  made  of  the  proper 
ratio  of  sand  and  cement  and  that  it  is  of  the  proper  consistency 
to  just  flow  into  the  joints,  and  that  after  mixing  it  is  kept  stirred 
until  used.  Repour  all  joints  where  necessary  to  completely  fill 
them. 

65.  Gutters  and  Expansion  Joints. — See  that  the  gutters  are  laid 
with  longitudinal  courses  of  brick  and  their  joints  filled  with  bitu- 
minous cement  as  provided  in  the  specifications. 

WOOD-BLOCK  PAVEMENT 

66.  Foundation. — The  instructions  relating  to  the  preparation  of 
the  sub-foundation  and  the  concrete  foundation  already  given  apply 
to  wood-block  pavement. 

67.  Inspection  of  Blocks. — However  carefully  the  lumber  may  have 
been  inspected  before  its  manufacture  into  blocks,  the  subsequent 
seasoning,  treatment,  handling  and  exposure  to  the  weather  will 
develop  many  defects  and  you  will  need  to  observe  the  delivered 
blocks  closely,  either  before  or  after  they  are  set,  and  reject  those 
that  do  not  comply  with  the  specifications.     The  principal  defects 
that  you  will  be  able  to  detect  after  the  blocks  are  treated  are  the 
following:  Southern  pine  blocks  made  of  second-growth  or  inferior 
wood,  partly  shown  by  the  number  of  annual-growth  rings  per  inch. 
Blocks  having  a  less  number  of  these  annual-growth  rings  per  inch 
than  is  permitted  by  the  specifications  should  be  rejected.     The 
treated  blocks,  especially  when  they  are  exposed  to  the  weather  for 
some  time,  are  likely  to  develop  seasoning  cracks,  "shakes"  and  loose 
knots,  not  observable  in  the  lumber,  and  blocks  showing  these  to  an 
injurious  extent  should  be  rejected,  though  in  many  cases  the  de- 
fective part  may  be  split  off  and  the  remainder  of  the  block  used  for 
closers.     If  the  blocks  have  become  very  dry  and  thoroughly  seasoned 
out,  they  should  be  well  sprinkled  with  water  about  twenty-four 
hours  before  they  are  to  be  set,  to  forestall  excessive  swelling  and 
"  humping  "  when  a  rain  storm  comes  upon  the  new  pavement. 

68.  Mortar  Bed. — It  is  the  common  practice  in  preparing  the  mor- 


INSTRUCTIONS  TO  INSPECTORS       113 

tar  for  the  mortar  bed  under  the  blocks  to  simply  dampen  the  mixed 
sand  and  cement  so  that  it  may  still  be  spread  and  handled  like  damp 
sand.  See  that  sufficient  water  is  used  to  make  a  moderately  stiff 
mortar,  suitable  for  being  worked  with  a  trowel.  This  mortar  should 
be  prepared  in  sufficiently  small  quantities  at  a  time  to  insure  that 
it  will  not  begin  to  set  before  the  blocks  be  placed  in  it  and  rammed. 

69.  Setting  the  Blocks. — The  setting  of  the  wooden  blocks  is  a 
comparatively  simple  operation  and  the  specifications  are  sufficiently 
full  and  clear  for  your  guidance.     See  that  the  blocks  are  so  set  that 
their  tops,  after  the  ramming  is  completed,  shall  be  truly  in  the  pave- 
ment datum,  without  humps  or  depressions. 

70.  Filling  the  Joints. — See  that  the  sand  used  is  perfectly  dry, 
fine  and  clean,  and  that  it  is  swept  about  on  the  pavement  until  the 
joints  are  completely  filled. 

BITUMINOUS  CONCRETE  PAVEMENT 

71.  Preparation  of  Foundation. — Where  a  bituminous  concrete 
wearing  surface  is  to  be  placed  upon  an  old  pavement  or  Macadam 
road  the  specifications  must  be  closely  followed.     A  good  foundation 
is  as  necessary,  if  good  results  are  to  be  attained,  as  in  the  case  of 
other  pavements.     The  dressing  down  of  high  points  and  the  filling 
up  of  depressions  in  the  old  pavement  should  be  carefully  done,  so 
that  the  bituminous  wearing  surface  shall  be  of  uniform  thickness, 
and  shall  be  rigidly  supported  at  all  points. 

72.  Bituminous  Concrete  Surface. — The  instructions  given  for 
the  manufacture  and  laying  of  sheet  asphalt  pavement  should  be 
followe4  here  insofar  as  they  are  applicable. 

HYDRAULIC  CONCRETE  ROADWAY  PAVEMENT 

73.  Like  other  structures  made  of  hydraulic  concrete,  the  utility 
and  durability  of  concrete  roadway  pavement  depends  largely  upon 
the  good  quality  of  the  materials  used  and  the  skill  and  fidelity  with 
which  the  work  is  done.     It  is  especially  important  that  the  second, 
or  surface,  course  of  the  concrete  shall  be  made  and  placed  in  strict 
accordance  with  the  specifications  and  that  a  high  degree  of  uni- 
formity shall  be  secured  in  the  composition,  consistency  and  work- 
manship of  that  part  of  the  work. 

74.  Sub -foundation  and  Foundation. — The  preparation  of  the  sub- 
foundation  will  be  the  same  as  for  other  pavements,  and  the  first^or 


1 1 4  STREET  ROA DWAY  PA VEMENTS 

foundation  course,  of  concrete,  will  be  constructed  as  in  the  case  of 
the  concrete  foundation  for  other  pavements. 

75.  Material  for  Surface-course. — It  may  be  assumed  that,  in 
general,  the  materials  intended  to  be  used  on  the  work  have  been 
inspected  and  approved  by  the  Engineer,  but  this  should  not  prevent 
you  from  calling  his  attention  to  any  defective  or  inferior  materials 
that  may  be  delivered  on  the  street  when  the  work  is  begun,  or 
thereafter,  and  preventing  the  use  of  any  materials  that  are  not  fully 
up  to  the  requirements  of  the  specifications. 

76.  Mixing  the  Surface  Course. — See  that  the  cement  sand  and 
stone  are  proportioned  accurately  and  that  the  quantity  of  water 
used  with  each  batch  is  measured,  so  as  to  make  the  concrete  of 
uniform  consistency.     Do  not  permit  any  defective  batches  of  con- 
crete to  be  used  in  the  suiface  course — if  suitable  for  the  bottom 
course  they  may  be  used  in  it.     Care  in  this  respect  is  particularly 
necessary  with  machine-mixed  concrete  where  the  machine  is  not 
working  normally  or  the  men  operating  it  are  careless  or  unskillful. 

77.  Placing   Surface   Course   Concrete. — See   that   the   surface 
course  is  placed,  graded  and  rammed  before  the  bottom  course  concrete 
begins  to  set.     This  is  imperative.     Also  that  the  concrete  is  dis- 
tributed and  graded  in  such  a  way  as  will  not  separate  or  segregate 
the  mortar  from  the  stone;  that  the  grading  of  the  surface  is  so  accu- 
rate that  it  will  not  be  necessary  later  to  add  additional  concrete 
to  that  already  graded  and  rammed;  that  the  ramming  is  thorough 
and  uniform  over  the  whole  surface,  and  that  the  rolling  is  well 
done. 

78.  Expansion  Joints. — Care  should  be  taken  to  have  the  expan- 
sion joints  made  as  the  specifications  require.     See  that  they  extend 
entirely  through  both  courses  of  concrete;  that  the  corners  are  prop- 
erly compacted  and  troweled;  that  the  joints  are  kept  clean  until 
they  are  filled  with  the  bituminous  cement,  and  are  completely 
filled  with  the  cement. 

79.  Care  of  Finished  Work. — Do  not  permit  the  completed  work 
to  be  disturbed  by  travel  over  it,  and  see  that  the  concrete  is  kept 
moist,  until  it  shall  be  set  up  hard,  and  that  the  street  is  not  opened 
for  travel  until  the  engineer  so  directs. 

CONCRETE  COMBINED  CURB  AND  GUTTER 

80.  General. — The  specifications  for  the  construction  of  Hydraulic 
Concrete  Combined  Curb  and  Gutter  are  quite  full  and  clear  and  the 


INSTRUCTIONS  TO  INSPECTORS 


115 


duty  of  the  inspector  will  consist  mainly  in  seeing  that  they  are 
faithfully  carried  out. 

81.  Concrete. — As  in  other  concrete  construction,  the  utility  of 
the  work  depends  largely  on  the  care  and  skill  with  which  the  con- 
crete is  made  and  placed.  See  that  the  prescribed  quality  and  ratio 
of  materials  are  used  and  that  the  concrete  is  thoroughly  mixed 
and  properly  placed  in  the  forms  and  well  tamped.  Especial  care 
is  necessary  to  secure  a  continuous  and  satisfactory  exposed  surface 
by  forking  and  working  the  mortar  into  contact  with  the  forms, 
which  must  be  placed  and  maintained  in  true  line  and  surface. 


Concrete  Combined 
Curb  and  Gutter 


Trench 

Filled  with 

Broken  Stone 


82.  Removing  Forms. — Good  judgment  is  required  as   to   the 
proper  time  to  remove  the  forms.     They  must  remain  until  the 
concrete  has  set  hard  enough  to  be  fully  self-sustaining,  but  before 
it  has  set  so  hard  that  the  wire  brush  will  have  no  effect  on  the 
surface. 

83.  Corner  Protection. — See  that  the  metallic  corner  or  nose 
piece  is  correctly  placed  and  that  it  is  solidly  anchored  by  and  fully 
embedded  in  the  body  of  the  concrete. 


1 1 6  STREET  ROA  DWA  Y  PA  VEMENTS 

84.  Patching. — The  practice  of  patching  up  cavities  or  irregu- 
larities in  the  exposed  face  of  the  curb  and  gutter  with  neat  mortar, 
or  dressing  the  surface  with  dry  cement,  must  not  be  permitted. 
If  a  section  of  the  curb  is  found,  when  the  forms  are  removed,  to  be 
imperfect,  the  whole  section  must  be  removed  and  replaced. 

HYDRAULIC  CEMENT  SIDEWALKS 

85.  General. — While    the  work  of   constructing   concrete  side- 
walk is  comparatively  simple  it  is  often  carelessly  and  unskillfully 
done.     The  things  that  need  most  attention  by  the  inspector  are  the 
following : 

86.  Materials. — The  materials  used  in  the  work  must  be  fully 
up  to  the  quality  called  for  by  the  specifications.     This  applies 
more  particularly  to  the  cement  and  sand.     These  are  not  always 
properly  tested  by  the  engineer  and  you  should  frequently  make 
samples  of  stiff  mortar  (i  cement,  2  sand)  and  set  them  aside  for 
observation.     If  they  do  not,  in  summer  weather,  become  very 
hard  at  the  end  of  nine  hours,  the  fact  should  be  reported  to  the 
engineer. 

87.  Drainage. — See  that  the  necessary  grading  is  properly  done 
and  that  the  drainage  course  is  made  of  suitable  material  properly 
compacted.     See  that  drain  tiles  are  properly  laid  and  connected 
as  designed  by  the  engineer.     If  cinders  are  used  for  the  drainage 
course,  see  that  they  are  screened  to  remove  ashes  and  fine  material, 
and  that  they  are  thoroughly  drenched  with  water  at  least  five 
days  before  they  are  placed  in  the  walk. 

88.  Two-course  Work. — If  the  sidewalk  is  laid  in  two  courses, 
see  that  the  surface-course  is  put  on  and  tamped  before  the  bottom- 
course  concrete  has  begun  to  set.     This  requirement  must  be  strictly 
enforced. 

89.  Finishing  the  Surface. — Dry  or  pure  cement  must  not  be 
used  for  trimming  up  or  smoothing  off  the  surface  of  the  walk. 
After  the  surface  has  been  properly  completed  by  straight-edge 
and  trowel,  see  that  the  wire  broom  is  used  as  directed  to  remove 
the  glaze  and  to  slightly  roughen  the  surface. 

See  that  the  expansion  joints  are  made  as  specified,  and  that  they 
extend  entirely  through  both  courses  of  concrete. 

90.  See  that  the  walk,  after  completion  is  properly  protected 
from  injury  and  from  frost,  and  that  the  concrete  is  kept  moist 
until  it  becomes  well  set. 


UNIVEKSITV  0, 


30w  6, 


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10    J 


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